Systems and methods for wireless communication of packets having a plurality of formats

ABSTRACT

Systems and methods for communicating packets having a plurality of formats are described herein. In some aspects, a signal (SIG) field in the preamble of a packet may indicate whether an extension field, such as an extension SIG field or SIG-B field, is included in the packet. In another aspect, one or more detectors may be used to auto-detect packets formatted as one of at least two different formats based on a short training field (STF) of a received packet. In some aspects, along training field (LTF) in the preamble of a packet may indicate whether the payload is repetition coded.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/486,107 entitled “SYSTEMS ANDMETHODS FOR WIRELESS COMMUNICATION OF PACKETS HAVING A PLURALITY OFFORMATS” filed on May 13, 2011, the disclosure of which is herebyincorporated by reference in its entirety. This application additionallyclaims benefit under 35 U.S.C. §119(e) to U.S. Provisional PatentApplication No. 61/488,714 entitled “SYSTEMS AND METHODS FOR WIRELESSCOMMUNICATION OF PACKETS HAVING A PLURALITY OF FORMATS” filed on May 21,2011, the disclosure of which is hereby incorporated by reference in itsentirety. This application also claims benefit under 35 U.S.C. §119(e)to U.S. Provisional Patent Application No. 61/577,442 entitled “SYSTEMSAND METHODS FOR WIRELESS COMMUNICATION OF PACKETS HAVING A PLURALITY OFFORMATS” filed on Dec. 19, 2011, the disclosure of which is herebyincorporated by reference in its entirety. This application claimsbenefit under 35 U.S.C. §119(e) to U.S. Provisional Patent ApplicationNo. 61/580,613 entitled “SYSTEMS AND METHODS FOR WIRELESS COMMUNICATIONOF PACKETS HAVING A PLURALITY OF FORMATS” filed on Dec. 27, 2011, thedisclosure of which is hereby incorporated by reference in its entirety.This application claims benefit under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/585,557 entitled “SYSTEMS ANDMETHODS FOR WIRELESS COMMUNICATION OF PACKETS HAVING A PLURALITY OFFORMATS” filed on Jan. 11, 2012, the disclosure of which is herebyincorporated by reference in its entirety.

BACKGROUND

1. Field

The present application relates generally to wireless communications,and more specifically to systems and methods for communicating packetshaving a plurality of different formats.

2. Background

In many telecommunication systems, communications networks are used toexchange messages among several interacting spatially-separated devices.Networks may be classified according to geographic scope, which couldbe, for example, a metropolitan area, a local area, or a personal area.Such networks would be designated respectively as a wide area network(WAN), metropolitan area network (MAN), local area network (LAN), orpersonal area network (PAN). Networks also differ according to theswitching/routing technique used to interconnect the various networknodes and devices (e.g. circuit switching vs. packet switching), thetype of physical media employed for transmission wired vs. wireless),and the set of communication protocols used (e.g. Internet protocolsuite, SONET (Synchronous Optical Networking), Ethernet, etc.).

Wireless networks are often preferred when the network elements are trioand thus have dynamic connectivity needs, or if the network architectureis formed in an ad hoc, rather than fixed, topology. Wireless networksemploy intangible physical media in an unguided propagation mode usingelectromagnetic waves in the radio, microwave, infra-red, optical, etc.frequency bands. Wireless networks advantageously facilitate usermobility and rapid field deployment when compared to fixed wirednetworks.

The devices in a wireless network may transmit/receive informationbetween each other. The information may comprise packets, which in someaspects may be referred to as data units. The packets may includeoverhead information (e.g., header information, packet properties, etc.)that helps in routing the packet through the network, identifying thedata in the packet, processing the packet, etc., as well as data, forexample user data, multimedia content, etc. as might be carried in apayload of the packet.

After a packet is received, portions of the overhead or controlinformation in a packet may be used to determine parameters forprocessing data carried in the packet. The packet, however, may beformatted in a plurality of ways. Accordingly, it is advantageous for atransmitting node to be able to determine which format to use for agiven communication and to generate the communication. Similarly, it isadvantageous for a receiving node to be able to determine the format ofthe packet and process the data in the packet accordingly. Thus,improved systems, methods, and devices for communicating packets havinga plurality of formats are desired.

SUMMARY

The systems, methods, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this invention provide advantages that include improvedapproaches for communicating packets having a plurality of formats.

One aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises a receiver configured to receivea wireless communication comprising a physical layer preamble and apayload. The preamble may include a first field indicating whether thepreamble includes an extension field. The apparatus further comprises aprocessor configured to process the payload based on modulation codingparameters included in the first field when the indicator signifies thatthe preamble does not include the extension field, and configured toprocess the payload based on coding parameters included in the extensionfield when the indicator signifies that the preamble includes theextension field.

Another aspect of the disclosure provides a method for wirelesscommunication. The method comprises receiving a wireless communicationcomprising a physical layer preamble and a payload. The preambleincludes a first field indicating whether the preamble includes anextension field. The method further comprises processing the payloadbased on modulation coding parameters included in the first field whenthe indicator signifies that the preamble does not include the extensionfield, and processing the payload based on coding parameters included inthe extension field when the indicator signifies that the preambleincludes the extension field.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises means for receiving a wirelesscommunication comprising a physical layer preamble and a payload. Thepreamble may include a first field indicating whether the preambleincludes an extension field. The apparatus further comprises means forprocessing the payload based on modulation coding parameters included inthe first field when the indicator signifies that the preamble does notinclude the extension field, and means for processing the payload basedon coding parameters included in the extension field when the indicatorsignifies that the preamble includes the extension field.

Another aspect of the disclosure provides a computer readable mediumcomprising instructions that when executed cause an apparatus to receivea wireless communication comprising a physical layer preamble and apayload. The preamble may include a first field indicating whether thepreamble includes an extension field. The medium further comprisesinstructions that when executed cause an apparatus to process thepayload based on modulation coding parameters included in the firstfield when the indicator signifies that the preamble does not includethe extension field, and process the payload based on coding parametersincluded in the extension field when the indicator signifies that thepreamble includes the extension field.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises a processor configured togenerate a communication comprising a physical layer preamble and apayload and to determine whether to include an extension field in thepreamble. The preamble includes a first field indicating whether theextension field is included. The processor is configured to includemodulation coding parameters for the payload in the first field when itis determined not to include the extension field, and to include codingparameters for the payload in the extension field when it is determinedto include the extension field. The apparatus further comprises atransmitter configured to wirelessly transmit the generatedcommunication.

Another aspect of the disclosure provides a method of wirelesscommunication. The method comprises determining whether to include anextension field in a physical layer preamble of a communication,generating the communication, and wirelessly transmitting the generatedcommunication. The communication comprises the preamble and a payload,and the preamble includes a first field indicating whether the extensionfield is included. The generation may comprise including modulationcoding parameters for the payload in the first field when it isdetermined not to include the extension field, and including codingparameters for the payload in the extension field when it is determinedto include the extension field.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises means for determining whether toinclude an extension field in a physical layer preamble of acommunication, means for generating the communication, and means forwirelessly transmitting the generated communication. The communicationcomprises the preamble and a payload, and the preamble includes a firstfield indicating whether the extension field is included. The means forgenerating may comprise means for including modulation coding parametersfor the payload in the first field when it is determined not to includethe extension field, and means for including coding parameters for thepayload in the extension field when it is determined to include theextension field.

Another aspect of the disclosure provides a computer readable mediumcomprising instructions that when executed cause an apparatus todetermine whether to include an extension field in a physical layerpreamble of a communication, generate the communication, and wirelesslytransmit the generated communication. The communication may comprise thepreamble and a payload, and the preamble may include a first fieldindicating whether the extension field is included. The generation maycomprise including modulation coding parameters for the payload in thefirst field when it is determined not to include the extension field,and including coding parameters for the payload in the extension fieldwhen it is determined to include the extension field.

One aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises a receiver configured towirelessly receive data packets having at least two formats. Thereceiver comprises a first detector configured to detect data packets ofat least one of the two formats and a second detector configured todetect data packets of another of the two formats. The apparatus furthercomprises a processor configured to process a received data packet basedat least in part on whether the received data packet was detected by thefirst detector or the second detector.

Another aspect of the disclosure provides a method for wirelesscommunication. The method comprises wirelessly receiving a data packethaving one of at least two formats, detecting a format of the receiveddata packet using one of at least two detectors configured to detectrespective data packet formats, and processing the received data packetbased on the detected format.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises means for wirelessly receiving adata packet having one of at least two formats, first means fordetecting whether the received data packet has a first format, secondmeans for detecting whether the received data packet has a secondformat, and means for processing the received data packet based on thefirst detecting means an the second detecting means.

Another aspect of the disclosure provides a computer readable mediumcomprising instructions that when executed cause an apparatus towirelessly receive a data packet having one of at least two formats,detect a format of the received data packet using one of at least twodetectors configured to detect respective data packet formats, andprocess the received data packet based on the detected format.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises a processor configured to selecta data packet format from at least two data packet formats comprising atraining field, and a transmitter configured to transmit a wirelesscommunication using the selected data packet format. The training fieldof one of the data packet formats includes a sequence repeated a greaternumber of times than in the training field of another of the data packetformats.

Another aspect of the disclosure provides a method of wirelesscommunication. The method comprises selecting a data packet format fromat least two data packet formats comprising a training field, andtransmitting a wireless communication using the selected data packetformat. The training field of one of the data packet formats includes asequence repeated a greater number of times than in the training fieldof another of the data packet formats.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises means for selecting a data packetformat from at least two data packet formats comprising a trainingfield, and means for transmitting a wireless communication using theselected data packet format. The training field of one of the datapacket formats includes a sequence repeated a greater number of timesthan in the training field of another of the data packet formats.

Another aspect of the disclosure provides a computer readable mediumcomprising instructions that when executed cause an apparatus to selecta data packet format from at least two data packet formats comprising atraining field, and transmit a wireless communication using the selecteddata packet format. The training field of one of the data packet formatsincludes a sequence repeated a greater number of times than in thetraining field of another of the data packet formats.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises a receiver configured to receiveat least a physical layer preamble of a wireless communication. Thepreamble includes a first field indicating whether the preamble alsoincludes an extension field. The apparatus further comprises a processorconfigured to abort reception of a remainder of the communication whenthe first field indicates that the preamble includes the extensionfield. The processor may be configured to determine whether theextension field is included based on the first field.

Another aspect of the disclosure provides a method of wirelesscommunication. The method comprises receiving at least a physical layerpreamble of a wireless communication. The preamble includes a firstfield indicating whether the preamble also includes an extension field.The method further comprises aborting reception of a remainder of thecommunication when the first field indicates that the preamble includesthe extension field. The method may further comprise determining whetherthe extension field is included based on the first field.

Another aspect of the disclosure provides an apparatus for wirelesscommunication. The apparatus comprises means for receiving at least aphysical layer preamble of a wireless communication. The preambleincludes a first field indicating whether the preamble also includes anextension field. The apparatus further comprises means for abortingreception of a remainder of the communication when the first fieldindicates that the preamble includes the extension field. The apparatusmay further comprise means for determining whether the extension fieldis included based on the first field.

Another aspect of the disclosure provides a computer readable mediumcomprising instructions that when executed cause an apparatus to receiveat least a physical layer preamble of a wireless communication. Thepreamble includes a first field indicating whether the preamble alsoincludes an extension field. The instructions further cause theapparatus to abort reception of a remainder of the communication whenthe first field indicates that the preamble includes the extensionfield. The instructions may further cause the apparatus to determinewhether the extension field is included based on the first field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communication system inwhich aspects of the present disclosure may be employed.

FIG. 2 illustrates various components that may be utilized in a wirelessdevice that may be employed within the wireless communication system ofFIG. 1.

FIG. 3 illustrates various components that may be utilized in thewireless device of FIG. 2 to transmit wireless communications.

FIG. 4 illustrates various components that may be utilized in thewireless device of FIG. 2 to receive wireless communications.

FIG. 5 is a functional block diagram of an example MIMO system that maybe implemented in wireless devices such as the wireless device of FIG. 2to transmit wireless communications.

FIG. 6 is a functional block diagram of an example MIMO system that maybe implemented in wireless devices such as the wireless device of FIG. 2to receive wireless communications.

FIG. 7 is a block diagram showing an example structure of a preamble andpayload of a physical layer packet.

FIG. 8A is a block diagram showing an example structure of a preambleand payload of a physical layer packet for transmission over a bandwidthof substantially 1 MHz.

FIG. 8B is a block diagram showing an example structure of a preambleand payload of a physical layer packet for transmission over a bandwidthof substantially 2 MHz according to a single user mode.

FIG. 8C is a block diagram showing an example structure of a preambleand payload of a physical layer packet for transmission over a bandwidthof substantially 2 MHz according to a multi user mode.

FIG. 9 illustrates an example of a format of a packet having a signalfield.

FIG. 10 illustrates an example of a format of a packet having a signalfield and an extension field.

FIG. 11 illustrates an example of a format of a packet having a signalfield.

FIG. 12 illustrates an example of the signal field of FIG. 9 or 10.

FIG. 13A illustrates an example of the signal field of FIG. 9 or 10.

FIG. 13B illustrates an example of the signal field of FIG. 9 or 10.

FIG. 14 illustrates an example of the signal field of FIG. 9 or 10.

FIG. 15 illustrates an example of the extension field of FIG. 10.

FIG. 16 illustrates an example of the extension field of FIG. 10.

FIG. 17 illustrates an example format of a packet haying a signal fieldand an extension field.

FIG. 18 illustrates an example packet format.

FIGS. 19A and 19B illustrate example formats of packets having one ormore signal fields.

FIG. 20 illustrates an example of a signal field in FIG. 19A or 19B.

FIG. 21 illustrates an example of a signal field in FIG. 19B.

FIGS. 22A, 22B, and 22C illustrate example formats of packets having oneor more signal fields.

FIG. 23 illustrates an example of a signal field of FIGS. 22A-22C.

FIG. 24 illustrates an example of a signal field of FIG. 22A or 22B.

FIGS. 25A and 25B illustrate example formats of packets having one ormore signal fields.

FIG. 26 illustrates an example of a signal field of FIGS. 25A and 25B.

FIG. 27 illustrates an example of an extension field of FIGS. 25A and25B.

FIG. 28 illustrates an aspect of a method for transmitting a packet.

FIG. 29 is a functional block diagram of an example wireless device thatmay be employed within the wireless communication system of FIG. 1.

FIG. 30 illustrates an aspect of a method for receiving a packet.

FIG. 31 is a functional block diagram of an example wireless device thatmay be employed within the wireless communication system of FIG. 1.

FIG. 32 illustrates various example components that may be utilized inthe receiver of FIG. 2.

FIG. 33 illustrates an example of the signal field of FIG. 11.

FIG. 34 illustrates an aspect of a method for transmitting a packet.

FIG. 35 is a functional block diagram of an example wireless device thatmay lie employed within the wireless communication system of FIG. 1.

FIG. 36 illustrates an aspect of a method for receiving a packet.

FIG. 37 is a functional block diagram of an example wireless device thatmay be employed within the wireless communication system of FIG. 1.

FIG. 38 illustrates an aspect of a method for receiving a portion of apacket.

FIG. 39 is a functional block diagram of an example wireless device thatmay be employed within the wireless communication system of FIG. 1.

FIG. 40 illustrates an aspect of a method for transmitting a packet.

FIG. 41 is a functional block diagram of an example wireless device thatmay be employed within the wireless communication system of FIG. 1.

FIG. 42 illustrates an aspect of a method for receiving a portion of apacket,

FIG. 43 is a functional block diagram of an example wireless device thatmay be employed within the wireless communication system of FIG. 1.

DETAILED DESCRIPTION

Various aspects of the novel systems, apparatuses, and methods aredescribed more fully hereinafter with reference to the accompanyingdrawings. The teachings disclosure may, however, be embodied in manydifferent forms and should not be construed as limited to any specificstructure or function presented throughout this disclosure. Rather,these aspects are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the disclosure to thoseskilled in the art. Based on the teachings herein one skilled in the onshould appreciate that the scope of the disclosure is intended to coverany aspect of the novel systems, apparatuses, and methods disclosedherein, whether implemented independently of or combined with any otheraspect of the invention. For example, an apparatus may be implemented ora method may be practiced using any number of the aspects set forthherein. In addition, the scope of the invention is intended to coversuch an apparatus or method which is practiced using other structure,functionality, or structure and functionality in addition to or otherthan the various aspects of the invention set forth herein. It should beunderstood that any aspect disclosed herein my be embodied by one ormore elements of a claim.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

Wireless network technologies may include various types of wirelesslocal area networks (WLANs). A WLAN may be used to interconnect nearbydevices together, employing widely used networking protocols. Thevarious aspects described herein may apply to any communicationstandard, such as WiFi or, more generally, any member of the IEEE 802.11family of wireless protocols. For example, the various aspects describedherein may be used as part of the IEEE 802.11ah protocol, which usessub-1 GHz bands.

In some aspects, wireless signals in a sub-gigahertz band may betransmitted according to the 802.11ah protocol using orthogonalfrequency-division multiplexing (OFDM), direct-sequence spread spectrum(DSSS) communications, a combination of OFDM and DSSS communications, orother schemes. Implementations of the 802.11ah protocol may be used forsensors, metering, and smart grid networks. Advantageously, aspects ofcertain devices implementing the 802.11ah protocol may consume lesspower than devices implementing other wireless protocols, and/or may beused to transmit wireless signals across a relatively long range, forexample about one kilometer or longer.

Certain of the devices described herein may further implement MultipleInput Multiple Output (MIMO) technology and be implemented as part ofthe 802.11ah standard. A MIMO system employs multiple (N_(T)) transmitantennas and multiple (N_(R)) receive antennas for data transmission. AMIMO channel formed by the N_(T) transmit and N_(R) receive antennas maybe decomposed into N_(s) independent channels, which are also referredto as spatial channels or streams, where N_(S)≦min{N_(T), N_(R)}. Eachof the N_(S) independent channels corresponds to a dimension. The MIMOsystem can provide improved performance (e.g., higher throughput and/orgreater reliability) if the additional dimensionalities created by themultiple transmit and receive antennas are utilized.

In some implementations, a WLAN includes various devices which are thecomponents that access the wireless network. For example, there may betwo types of devices: access points (“APs”) and clients (also referredto as stations, or “STAs”). In general, an AP serves as a hub or basestation for the WLAN and an STA serves as a user of the WLAN. Forexample, an STA may be a laptop computer, a personal digital assistant(PDA), a mobile phone, etc. In an example, an STA connects to an AP viaa WiFi (e.g., IEEE 802.11 protocol such as 802.11ah) compliant wirelesslink to obtain general connectivity to the Internet or to other widearea networks. In some implementations an STA may also be used as an AP.

An access point (“AP”) may also comprise, be implemented as, or known asa NodeB, Radio Network Controller (“RNC”), eNodeB, Base StationController (“BSC”), Base Transceiver Station (“BTS”), Base Station(“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, orsome other terminology.

A station “STA” may also comprise, be implemented as, or known as anaccess terminal (“AT”), a subscriber station, a subscriber unit, amobile station, a remote station, a remote terminal, a user terminal, auser agent, a user device, user equipment, or some other terminology. Insome implementations an access terminal may comprise a cellulartelephone, a cordless telephone, a Session Initiation Protocol (“SIP”)phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smartphone), acomputer (e.g., a laptop), a portable communication device, a headset, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a gaming device or system, a global positioning system device,or any other suitable device that is configured to communicate via awireless medium.

As discussed above, certain of the devices described herein mayimplement the 802.11ah standard, for example. Such devices, whether usedas an STA or AP or other device, may be used for smart metering or in asmart grid network. Such devices may provide sensor applications or beused in home automation. The devices may instead or in addition be usedin a healthcare context, for example for personal healthcare. They mayalso be used for surveillance, to enable extended-range Internetconnectivity (e.g. for use with hotspots), or to implementmachine-to-machine communications.

FIG. 1 illustrates an example of a wireless communication system 100 inwhich aspects of the present disclosure may be employed. The wirelesscommunication system 100 may operate pursuant to a wireless standard,for example the 802.11ah standard. The wireless communication system 100may include an AP 104, which communicates with STAs 106 a, 106 b, 106 c,106 d (collectively STAs 106).

A variety of processes and methods may be used for transmissions in thewireless communication system 100 between the AP 104 and the STAs 106.For example, signals may be sent and received between the AP 104 and theSTAs 106 in accordance with OFDM/OFDMA techniques. If this is the case,the wireless communication system 100 may be referred to as anOFDM/OFDMA system. Alternatively, signals may be sent and receivedbetween the AP 104 and the STAs 106 in accordance with CDMA techniques.If this is the case, the wireless communication system 100 may bereferred to as a CDMA system.

A communication link that facilitates transmission from the AP 104 toone or more of the STAs 106 may be referred to as a downlink (DL) 108,and a communication link that facilitates transmission from one or moreof the STAs 106 to the AP 104 may be referred to as an uplink (UL) 110.Alternatively, a downlink 108 may be referred to as a forward link or aforward channel, and an uplink 110 may be referred to as a reverse linkor a reverse channel.

The AP 104 may act as a base station and provide wireless communicationcoverage in a basic service area (BSA) 102. The AP 104 along with theSTAs 106 associated with the AP 104 and that use the AP 104 forcommunication may be referred to as a basic service set (BSS). It shouldbe noted that the wireless communication system 100 may not have acentral AP 104, but rather may function as a peer-to-peer networkbetween the STAs 106. Accordingly, the functions of the AP 104 describedherein may alternatively be performed by one or more of the STAs 106.

FIG. 2 illustrates various components that may be utilized in a wirelessdevice 202 that may be employed within the wireless communication system100. The wireless device 202 is an example of a device that may beconfigured to implement the various methods described herein. Forexample, the wireless device 202 may comprise the AP 104 or one of theSTAs 106 of FIG. 1.

The wireless device 202 may include a processor 204 which controlsoperation of the wireless device 202. The processor 204 may also bereferred to as a central processing unit (CPU). Memory 206, which mayinclude both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 204. A portion of thememory 206 may also include non-volatile random access memory (NVRAM).The processor 204 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 206. Theinstructions in the memory 206 may be executable to implement themethods described herein.

When the wireless device 202 is implemented or used as a transmittingnode, the processor 204 may be configured to select one of a pluralityof packet formats, and to generate a packet having that format. Forexample, the processor 204 may be configured to generate a packetcomprising a preamble, such as a physical layer preamble and a payloadand to determine whether to include an extension field in the preamble,as discussed in further detail below. The processor 204 may further beconfigured to generate a packet having a training field with a repeatedsequence.

When the wireless device 202 is implemented or used as a receiving node,the processor 204 may be configured to process packets having aplurality of formats. For example, the processor 204 may be configuredto process a payload of a packet based on a preamble of the packet. Insome aspects, the preamble includes an extension field, as discussed infurther detail below.

The processor 204 may comprise or be a component of a processing systemimplemented with one or more processors. The one or more processors maybe implemented with any combination of general-purpose microprocessors,microcontrollers, digital signal processors (DSPs), field programmablegate array (FPGAs), programmable logic devices (PLDs), controllers,state machines, gated logic, discrete hardware components, dedicatedhardware finite state machines, or any other suitable entities that canperform calculations or other manipulations of information.

The processing system may also include machine-readable media forstoring software. Software shall be construed broadly to mean any typeof instructions, whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise. Instructions mayinclude code (e.g., in source code format, binary code format,executable code format, or any other suitable format of code). Theinstructions, when executed by the one or more processors, cause theprocessing system to perform the various functions described herein.

The wireless device 202 may also include a housing 208 that may includea transmitter 210 and/or a receiver 212 to allow transmission andreception of data between the wireless device 202 and a remote location.The transmitter 210 and receiver 212 may be combined into a transceiver214. An antenna 216 may be attached to the housing 208 and electricallycoupled to the transceiver 214. The wireless device 202 may also include(not shown) multiple transmitters, multiple receivers, multipletransceivers, and/or multiple antennas.

The transmitter 210 may be configured to wirelessly transmit packetshaving a plurality of different formats. For example, the transmitter210 may be configured to transmit different types of packets generatedby the processor 204, discussed above.

The receiver 212 may be configured to wirelessly receive packets havinga plurality of different formats. In some aspects, the receiver 212 isconfigured to detect a type of a received packet, as discussed infurther detail below. For example, the receiver may implement anauto-detect procedure to determine a format of a received packet priorto the processing system processing the packet or a payload thereof.

The wireless device 202 may also include a signal detector 218 that maybe used to detect and quantify the level of signals received by thetransceiver 214. The signal detector 218 may detect such signals astotal energy, energy per subcarrier per symbol, power spectral density,and other signals. The wireless device 202 may also include a digitalsignal processor (DSP) 220 for use in processing signals. The DSP 220may be configured to generate a packet for transmission. In someaspects, the packet may comprise a physical layer data unit (PPDU).

The wireless device 202 may further comprise a user interface 222 insome aspects. The user interface 222 may comprise a keypad, amicrophone, a speaker, and/or a display. The user interface 222 mayinclude any element or component that conveys information to a user ofthe wireless device 202 and/or receives input from the user.

The various components of the wireless device 202 may be coupledtogether by a bus system 226. The bus system 226 may include a data bus,for example, as well as a power bus, a control signal bus, and a statussignal bus in addition to the data bus. The components of the wirelessdevice 202 may further be coupled together or accept or provide inputsto each other using some other mechanism.

Although a number of separate components are illustrated in FIG. 2, oneor more of the components may be combined or commonly implemented. Forexample, the processor 204 may be used to implement not only thefunctionality described above with respect to the processor 204, butalso to implement the functionality described above with respect to thesignal detector 218 and/or the DSP 220. Further, each of the componentsillustrated in FIG. 2 may be implemented using a plurality of separateelements. Furthermore, the processor 204 may be used to implement any ofthe components, modules, circuits, or the like described, or each may beimplemented using a plurality of separate elements.

For ease of reference in this disclosure, when the wireless device 202is configured as a transmitting node, it may hereinafter be referred toas a wireless device 202 t. Similarly, when the wireless device 202 isconfigured as a receiving node, it may hereinafter be referred to as awireless device 202 r. A device in the wireless communication system 100of FIG. 1 may implement only functionality of a transmitting node, onlyfunctionality of a receiving node, or functionality of both atransmitting node and a receive node.

The wireless device 202 t of FIG. 3 may comprise a modulator 302configured to modulate bits for transmission. For example, the modulator302 may determine a plurality of symbols from bits received from theprocessor 204 (FIG. 2) or the user interface 222 (FIG. 2), for exampleby mapping bits to a plurality of symbols according to a constellation.The bits may correspond to user data or to control information. In someaspects, the bits are received in codewords. In one aspect, themodulator 302 comprises a QAM (quadrature amplitude modulation)modulator, for example a 16-QAM modulator or a 64-QAM modulator. Inother aspects, the modulator 302 comprises a binary phase-shift keying(BPSK) modulator or a quadrature phase-shift keying (QPSK) modulator.

The wireless device 202 t may further comprise a transform module 304configured to convert symbols or otherwise modulated bits from themodulator 302 into a time domain. In FIG. 3, the transform module 304 isillustrated as being implemented by an inverse fast Fourier transform(IFFT) module. In some implementations, there may be multiple transformmodules (not shown) that transform units of data of different sizes. Insome implementations, the transform module 304 may be itself configuredto transform units of data of different sizes. For example, thetransform module 304 may be configured with a plurality of modes, andmay use a different number of points to convert the symbols in eachmode. For example, the IFFT may have a mode where 32 points are used toconvert symbols being transmitted over 32 tones (i.e., subcarriers) intoa time domain, and a mode where 64 points are used to convert symbolsbeing transmitted over 64 tones into a time domain. The number of pointsused by the transform module 304 may be referred to as the size of thetransform module 304.

In FIG. 3, the modulator 302 and the transform module 304 areillustrated as being implemented in the DSP 320. In some aspects,however, one or both of the modulator 302 and the transform module 304are implemented in the processor 204 or in another element of thewireless device 202 (e.g., see description above with reference to FIG.2).

As discussed above, the DSP 320 may be configured to generate a dataunit for transmission. In some aspects, the modulator 302 and thetransform module 304 may be configured to generate a data unitcomprising a plurality of fields including control information and aplurality of data symbols. The fields including the control informationmay comprise one or more training fields, for example, and one or moresignal (SIG) fields. Each of the training fields may include a knownsequence of bits or symbols. Each of the SIG fields may includeinformation about the data unit, for example a description of a lengthor data rate of the data unit.

In some aspects, the DSP 320 is configured to insert one or moretraining fields between a plurality of data symbols. The DSP 320 maydetermine a position or location of the one or more training fields inthe data unit based on information received from the processor 204 (FIG.2), and/or stored in the memory 206 (FIG. 2) or in a portion of the DSP320. Inserting the training fields in the data unit will be discussed inadditional detail.

Returning to the description of FIG. 3, the wireless device 202 t mayfurther comprise a digital to analog converter 306 configured to convertthe output of the transform module into an analog signal. For example,the time-domain output of the transform module 306 may be converted to abaseband OFDM signal by the digital to analog converter 306. The digitalto analog converter 306 may be implemented in the processor 204 or inanother element of the wireless device 202 of FIG. 2. In some aspects,the digital to analog converter 306 is implemented in the transceiver214 (FIG. 2) or in a data transmit processor.

The analog signal may be wirelessly transmitted by the transmitter 310.The analog signal may be further processed before being transmitted bythe transmitter 310, for example by being filtered or by beingupconverted to an intermediate or carrier frequency. In the aspectillustrated in FIG. 3, the transmitter 310 includes a transmit amplifier308, Prior to being transmit, the analog signal may be amplified by thetransmit amplifier 308. In some aspects, the amplifier 308 comprises alow noise amplifier (LNA).

The transmitter 310 is configured to transmit one or more packets ordata units in a wireless signal based on the analog signal. The dataunits may be generated using the processor 204 (FIG. 2) and/or the DSP320, for example using the modulator 302 and the transform module 304 asdiscussed above. Data units that may be generated and transmitted asdiscussed above are described in additional detail in this disclosure.

In some aspects, the transmitter 310 is configured to transmit the dataunits over a bandwidth of approximately 2.5 MHz or 1.25 MHz, or lower.When using such bandwidths, transmission of the data unit may beperformed over a relatively lengthy period of time. For example, a dataunit composed of 500 bytes may be transmitted over a period ofapproximately 11 milliseconds. Such transmission is approximatelysixteen times slower than comparable transmissions implemented pursuantto the 802.11ac standard over bandwidths of approximately 20 MHz.

FIG. 4 illustrates various components that may be utilized in thewireless device 202 of FIG. 2 to receive wireless communications. Thecomponents illustrated in FIG. 4 may be used, for example, to receiveOFDM communications. For example, the components illustrated in FIG. 4may be used to receive data units transmitted by the componentsdiscussed above with respect to FIG. 3.

The receiver 412 of wireless device 202 r is configured to receive oneor more packets or data units in a wireless signal. Data units that maybe received and decoded or otherwise processed as discussed below aredescribed in additional detail in this disclosure.

In some aspects, the receiver 412 is configured to receive the dataunits over a bandwidth of approximately 2.5 MHz or 1.25 MHz, or lower.When using such bandwidths, reception of the data unit may be performedover a relatively lengthy period of time, for example approximately 11milliseconds when the data unit is composed of 500 bytes. During thistime, the channel over which the data unit is received may be changing.For example, conditions of the channel may change due to movement of thewireless device 202 r or of a device transmitting the data unit, or dueto weather or other environmental conditions such as the introduction ofvarious obstacles. In such circumstances, information near the end ofthe data unit may not be correctly decoded if the wireless device 202 ruses settings determined when reception of the data unit began. Asdescribed in additional detail below, however, the wireless device 202 rmay use the training fields interposed between the plurality of datasymbols to form an updated estimate of the channel in order to properlydecode one or more of the data symbols.

In the aspect illustrated in FIG. 4, the receiver 412 includes a receiveamplifier 401. The receive amplifier 401 may be configured to amplifythe wireless signal received by the receiver 412. In some aspects, thereceiver 412 is configured to adjust the gain of the receive amplifier401 using an automatic gain control (AGC) procedure. In some aspects,the automatic gain control uses information in one or more receivedtraining fields, such as a received short training field (STF), forexample, to adjust the gain. Those having ordinary skill in the art willunderstand methods for performing AGC. In some aspects, the amplifier401 comprises an LNA.

The wireless device 202 r may comprise an analog to digital converter410 configured to convert the amplified wireless signal from thereceiver 410 into a digital representation thereof. Further to beingamplified, the wireless signal may be processed before being convertedby the digital to analog converter 410, for example by being filtered ordownconverted to an intermediate or baseband frequency. The analog todigital converter 410 may be implemented in the processor 204 or inanother element of the wireless device 202 (FIG. 2). In some aspects,the analog to digital converter 410 is implemented in a transceiver orin a data receive processor.

The wireless device 202 r may further comprise a transform module 404configured to convert the representation of the wireless signal into afrequency spectrum. In FIG. 4, the transform module 404 is illustratedas being implemented by a fast Fourier transform (FFT) module. In someaspects, the transform module may identify a symbol for each point thatit uses. As described above with reference to transform module 304 ofFIG. 3, the transform module 404 may be configured with a plurality ofmodes, and may use a different number of points to convert the signal ineach mode. For example, the transform module 401 may have a mode where32 points are used to convert a signal received over 32 tones into afrequency spectrum, and a mode where 64 points are used to convert asignal received over 64 tones into a frequency spectrum. The number ofpoints used by the transform module 404 may be referred to as the sizeof the transform module 404. In some aspects, the transform module 404may identify a symbol for each point that it uses.

The wireless device 202 r may further comprise a channel estimator andequalizer 405 configured to form an estimate of the channel over whichthe data unit is received, and to remove certain effects of the channelbased on the channel estimate. For example, the channel estimator may beconfigured to approximate a function of the channel, and the channelequalizer may be configured to apply an inverse of that function to thedata in the frequency spectrum.

In some aspects, the channel estimator and equalizer 405 usesinformation in one or more received training fields, such as a longtraining field (LTF) for example, to estimate the channel. The channelestimate may be formed based on one or more LTFs received at thebeginning of the data unit. This channel estimate may thereafter be usedto equalize data symbols that follow the one or more LTFs. After acertain period of time or after a certain number of data symbols, one ormore additional LTFs may be received in the data unit. The channelestimate may be updated or a new estimate formed using the additionalLTFs. This new or updated channel estimate may be used to equalize datasymbols that follow the additional LTFs. In some aspects, the new orupdated channel estimate is used to re-equalize data symbols precedingthe additional LTFs. Those having ordinary skill in the art willunderstand methods for forming a channel estimate.

The wireless device 202 r may further comprise a demodulator 406configured to demodulate the equalized data. For example, thedemodulator 406 may determine a plurality of bits from symbols output bythe transform module 404 and the channel estimator and equalizer 405,for example by reversing a mapping of bits to a symbol in aconstellation. The bits may be processed or evaluated by the processor204 (FIG. 2), or used to display or otherwise output information to theuser interface 222 (FIG. 2). In this way, data and/or information may bedecoded. In some aspects, the bits correspond to codewords. In oneaspect, the demodulator 406 comprises a QAM (quadrature amplitudemodulation) demodulator, for example a 16-QAM demodulator or a 64-QAMdemodulator. In other aspects, the demodulator 406 comprises a binaryphase-shift keying (BPSK) demodulator or a quadrature phase-shift keying(QPSK) demodulator.

In FIG. 4, the transform module 404, the channel estimator and equalizer405, and the demodulator 406 are illustrated as being implemented in theDSP 420. In some aspects, however, one or more of the transform module404, the channel estimator and equalizer 405, and the demodulator 406are implemented in the processor 204 or in another element of thewireless device 202 (e.g., see description above with reference to FIG.2).

As discussed above, the wireless signal received at the receiver 412comprises one or more data units. Using the functions or componentsdescribed above, the data units or data symbols therein may be decodedevaluated or otherwise evaluated or processed. For example, theprocessor 204 (FIG. 2) and/or the DSP 420 may be used to decode datasymbols in the data units using the transform module 404, the channelestimator and equalizer 405, and the demodulator 406.

Data units exchanged by the AP 104 and the STA 106 may include controlinformation or data, as discussed above. At the physical (PHY) layer,these data units may be referred to as physical layer protocol dataunits (PPDUs). In some aspects, a PPDU may be referred to as a packet orphysical layer packet. Each PPDU may comprise a preamble and a payload.The preamble may include training fields and a SIG field. The payloadmay comprise a Media Access Control (MAC) header or data for otherlayers, and/or user data, for example. The payload may be transmittedusing one or more data symbols. The systems, methods, and devices hereinmay utilize data units with training fields that are also interposedbetween data symbols in the payload.

The wireless device 202 t shown in FIG. 3 shows an example of a singletransmit chain to be transmitted over an antenna. The wireless device202 r shown in FIG. 4 shows an example of a single receive chain to bereceived over an antenna. In some implementations, the wireless devices202 t and 202 r may implement a portion of a MIMO system using multipleantennas to simultaneously transmit data.

FIG. 5 is a functional block diagram of a MIMO system that may beimplemented in wireless devices such as the wireless device 202 of FIG.2 to transmit and receive wireless communications. The MIMO system maymake use of some or all of the components described with reference toFIG. 3. Bits for transmission that are to be received at an output ofthe receiver are provided to an encoder 504. The encoder 504 may apply aforward error correcting (FEC) code on the bit stream. The FEC code maybe a block code, a convolutional code, or the like. The encoded bits areprovided to an interleaving system 505 that distributes the encoded bitsinto N transmit streams.

The interleaving system 505 includes a stream parser 506 that parses aninput bit stream from the encoder 504 to N spatial stream interleavers508 a, 508 b, and 508 n (collectively interleaver 508). The streamparser 506 may be provided with the number of spatial streams and parsebits on a round-robin basis. Other parsing functions may also be used.One parsing function that may be used is k_(n)=N_(tX)*k+n (i.e.,round-robin with one bit per spatial stream, then on to the next spatialstream where k_(n) is the input bit index and N_(TX) is the number oftransmitters/spatial streams). Another more general function f(k,n) mayalso be used, for example, sending two bits to a spatial stream, thenmoving on to the next spatial stream. Each interleaver 508 a, 508 b, and508 n may each thereafter distribute bits so that errors may berecovered due to fading or other channel conditions.

Each transmit stream may then be modulated by a modulator 502 a, 502 b,or 502 n. As described above with reference to FIG. 3, the bits may bemodulated using modulation techniques such as QPSK (Quaternary PhaseShift Keying) modulation, BPSK (mapping one bit at a time), 16-QAM(mapping group of six bits), 64-QAM, and the like. The modulated bitsfor each stream may be provided to transform modules 510 a, 510 b, and510 n. In some implementations, the transform modules 510 a, 510 b, and510 n may perform an inverse discrete time fourier transform (IDFT) toconvert the modulated bits from a frequency domain into a time domain.The transform modules 510 a, 510 b, and 510 n may operate according todifferent modes as described above with reference to FIG. 3. Forexample, the transform modules 510 a, 510 b, and 510 n may be configuredto operate according to a 32 point mode or a 64 point mode. In someimplementations, the modulated bits may be encoded using space timeblock coding (STBC) and spatial mapping may be performed before beingprovided to transform modules 510 a, 510 b, and 510 n. After themodulated bits have been converted into time domain signals for eachspatial stream, the time domain signal may be converted into an analogsignal via converters 512 a, 512 b, and 512 n as described above withreference to FIG. 3. The signals may then be transmitted usingtransmitters 514 a, 514 h, and 514 c and using antennas 516 a, 516 b, or516 n, into a wireless radio space over a desired frequency bandwidth(e.g., 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz, or higher).

In some embodiments, antennas 516 a, 516 b, and 516 n are distinct andspatially separated antennas. In other embodiments, distinct signals maybe combined into different polarizations off of fewer than N antennas.An example of this is where spatial rotation or spatial spreading isdone and multiple spatial streams are mapped on a single antenna.Further, distinct spatial streams can be organized in different manners.For example, a transmit antenna may carry data from more than onespatial stream or several transmit antennas may carry data from aspatial stream. For example, consider the case of a transmitter withfour transmit antennas and two spatial streams. Each spatial stream canbe mapped onto two transmit antennas, so two antennas are carrying datafrom just one spatial stream.

FIG. 6 is a functional block diagram of an exemplary MIMO system thatmay be implemented in wireless devices such as the wireless device 202of FIG. 2 to receive wireless communications. The MIMO system may makeuse of some or all of the components described with reference to FIG. 4.The wireless device 202 r may be configured to receive transmissionsfrom the antennas 516 a, 516 b, and 516 n of FIG. 5. A wireless device202 r receives signals from the channel at N antennas 518 a, 518 b, and518 n or 618 a, 618 b, and 618 n (counting separate polarizations, asappropriate) coupled to N receive circuits. The signals are thenprovided to receivers 620 a, 620 b, and 620 n that each may include anamplifier configured to amplify the received signals. The signals maythen be converted into a digital form via converters 622 a, 622 b, and622 n.

Converted signals may then be converted into a frequency spectrum viatransform modules 624 a, 624 b, and 624 n. As described above, thetransform modules 624 a, 624 b, and 624 n may operate according tovarious modes and according to the size and bandwidth used (e.g., 32point 64 point, etc.). The transformed signals may be provided torespective channel estimator and equalizer blocks 626 a, 626 b, and 626n that may function similarly as described above with reference to FIG.4. After channel estimation, the outputs may be provided to a MIMOdetector 628 (e.g., corresponding to MIMO detector 528 of FIG. 5) whichmay thereafter provide its output to demodulators 630 a, 630 b, and 630n which may demodulate the bits according to one of the modulationtechniques as described above. Demodulated bits may then be provided todeinterleavers 632 a, 632 b, and 632 n which may pass bits into a streamde-parser 634 which may provide the bits into a single bit stream into adecoder 636 (e.g., corresponding to decoder 536 of FIG. 5) that maydecode the bits into an appropriate data stream.

As described above, data units exchanged by the AP 104 and the STA 106may include control information or data in the form of physical (PHY)layer packets or physical layer protocol data units (PPDUs).

FIG. 7 is a block diagram showing an example structure of a preamble 702and payload 710 of a physical layer packet 700. The preamble 702 mayinclude a short training field (STF) 704 that includes an STF sequenceof known values. In some aspects, the STF may be used for packetdetection (e.g., to detect the start of a packet) and for coarsetime/frequency estimation. The STF sequence may be optimized to have alow PAPR and include a subset of non-zero tones with a particularperiodicity. The STF 704 may span one or multiple OFDM symbols. In someaspects, the preamble 702 may include a long training field (LTF) 706that may span one or multiple OFDM symbols and may include one or moreLTF sequences of known non-zero values. The LTF may be used for channelestimation, fine time/frequency estimation, and mode detection. Further,in some aspects, the preamble 702 may include a signal field (SIG) 708as described above that may include a number of bits or values used inone aspect for mode detection purposes and determination of transmissionparameters.

Certain implementations described herein may be directed to wirelesscommunication systems that may be used for smart metering or in a smartgrid network. These wireless communication systems may be used toprovide sensor applications or in home automation. Wireless devices usedin such systems may instead or in addition be used in a healthcarecontext, for example, for personal healthcare. They may also be used forsurveillance, to enable extended-range Internet connectivity (e.g., foruse with hotspots), or to implement machine-to-machine communications.Accordingly, some implementations may use low data rates such asapproximately 150 Kbps. Implementations may further have increased linkbudget gains (e.g., around 20 dB) over other wireless communicationssuch as 802.11b. In accordance with low data rates, if wireless nodesare configured for use in a home environment, certain aspects may bedirected to implementations with good in-home coverage without poweramplification. Furthermore, certain aspects may be directed tosingle-hop networking without using a MESH protocol. In addition,certain implementations may result in significant outdoor coverageimprovement with power amplification over other wireless protocols,Furthermore, certain aspects may be directed to implementations that mayaccommodate large outdoor delay-spread and reduced sensitivity toDoppler. Certain implementations may achieve similar LO accuracy astraditional WiFi.

Accordingly, certain implementations are directed to transmitting andreceiving wireless signals in sub-gigahertz bands. In one aspect, thismay result in a propagation gain of, for example, 8.5 dB (e.g.,available due to 900 MHz vs. 2.4 GHz). In another aspect, obstructionloss may be reduced by using sub-gigahertz signal which may result in,for example, a 3 dB gain.

Certain implementations are further directed to sending wireless signalswith low bandwidths in sub-gigahertz bands. This may further allowachieving greater link budget gains over other wireless communicationsystems. For example, in one implementation, a symbol may be configuredto be transmitted or received using a bandwidth of 1 MHz. The wirelessdevice 202 of FIG. 2 may be configured to operate in one of severalmodes. In one mode, symbols such as OFDM symbols may be transmitted orreceived using a bandwidth of 1 MHz. In another mode, symbols may betransmitted or received using a bandwidth of 2 MHz. Additional modes mayalso be provided for transmitting or receiving symbols using a bandwidthof 4 MHz, 8 MHz, 16 MHz, and the like. The bandwidth may also bereferred to as the channel width.

Each mode may use a different number of tones/subcarriers fortransmitting the information. For example, in one implementation, a 1MHz mode (corresponding to transmitting or receiving symbols using abandwidth of 1 MHz) may use 32 tones. In one aspect, using a 1 MHz modemay provide for a 13 dB noise reduction as compared to a bandwidth suchas 20 MHz. In addition, low rate techniques may be used to overcomeeffects such as frequency diversity losses due to a lower bandwidthwhich could result in 4-5 dB losses depending on channel conditions. Togenerate/evaluate symbols sent or received using 32 tones, a transformmodule 304 or 404 as described in FIGS. 3 and 4 may be configured to usea 32 point mode (e.g., a 32 point IFFT or FFT). The 32 tones may beallocated as data tones, pilot tones, guard tones, and a DC tone. In oneimplementation, 24 tones may be allocated as data tones, 2 tones may beallocated as pilot tones, five tones may be allocated as guard tones,and 1 tone may be reserved for the DC tone. In this implementation, thesymbol duration may be configured to be 40 μs including cyclic prefix.

For example, a wireless device 202 t of FIG. 3 may be configured togenerate a packet for transmission via a wireless signal using abandwidth of 1 MHz. In one aspect, the bandwidth may be approximately 1MHz where approximately 1 MHz may be within a range of 0.8 MHz to 1.2MHz. The packet may be formed of one or more OFDM symbols having 32tones allocated as described using a DSP 320 (FIG. 3). A transformmodule 304 (FIG. 3) in a transmit chain may be configured as an IFFTmodule operating according to a thirty-two point mode to convert thepacket into a time domain signal. A transmitter 310 (FIG. 3) may then beconfigured to transmit the packet.

Likewise, a wireless device 202 r of FIG. 4 may be configured to receivethe packet over a bandwidth of 1 MHz. In one aspect, the bandwidth maybe approximately 1 MHz where approximately 1 MHz may be within a rangeof 0.8 MHz to 1.2 MHz. The wireless device 202 r may include a DSP 420(FIG. 4) including a transform module 404 (FIG. 4) in a receive chainthat may be configured as an FFT module operating according to athirty-two point mode to transform the time domain signal into afrequency spectrum. A DSP 420 may be configured to evaluate the packet.The 1 MHz mode may support a modulation and coding scheme (MCS) for botha low data rate and a “normal” rate. According to some implementations,the preamble 702 may be designed for a low rate mode that offersreliable detection and improved channel estimation as will be furtherdescribed below. Each mode may be configured to use a correspondingpreamble configured to optimize transmissions for the mode and desiredcharacteristics.

In addition to a 1 MHz mode, a 2 MHz mode may additionally be availablethat may be used to transmit and receive symbols using 64 tones. In oneimplementation, the 64 tones may be allocated as 52 data tones, 4 pilottones, 1 DC tone, and 7 guard tones. As such, a transform module 304 or404 of FIGS. 3 and 4 may be configured to operate according to a 64point mode when transmitting or receiving 2 MHz symbols. The symbolduration may also be 40 μs including cyclic prefix. Additional modeswith different bandwidths (e.g., 4 MHz, 8 MHz, and 16 MHz) may beprovided that may use transform modules 304 or 404 operating in modes ofcorresponding different sizes (e.g., 128 point FFT, 256 point FFT, 512point FFT, etc.). In addition, each of the modes described above may beconfigured additionally according to both a single user mode and a multiuser mode. Wireless signals using bandwidths less than or equal to 2 MHzmay provide various advantages for providing wireless nodes that areconfigured to meet global regulatory constraints over a broad range ofbandwidth, power, and channel limitations.

In some aspects, the wireless device 202 of FIG. 2 is configured tooperate according to several wireless standards, for example, accordingto one of the 802.11 standards. In this configuration, the wirelessdevice 202 may have a mode for operating in a 20 MHz channel width inthe 2.4 GHz or 5 GHz band, as well as a mode for operating in a 40 MHzchannel width in the 2.4 GHz band. In another aspect, the wirelessdevice 202 is configured to operate pursuant to the 802.11ac standard.In this configuration, the wireless device 202 has a mode for operatingin each of a 20 MHz, 40 MHz, and 80 MHz channel width. Generally, thetransform module 304 or 404 may use 64 tones when the wireless device202, is operating in the 20 MHz band, may use 128 tones when thewireless device 202 is operating in the 40 MHz band, and may use 256tones when the wireless device 202 is operating in the 80 MHz band.

In some aspects, a controller (e.g., such as processor 204 or DSP 220 ofFIG. 2) is configured to adjust operation of the wireless device 202 ofFIG. 2 so as to operate in a sub-gigahertz band as described above. Inone implementation, to operate according to a mode such as 1 MHz, 2 MHz,4 MHz, etc. as described above, a controller may be configured todownclock one or more of the components in the wireless device 202 suchthat the wireless device 202 will operate in a 1 MHz, 2 MHz, 4 MHz, 8MHz, or 16 MHz. In addition, the processor 204 may be configured todownclock operation of one or more of the components in the wirelessdevice 202, such that the wireless device 202 will operate in modescorresponding to using bandwidths of 5 MHz, 2.5 MHz, 1.25 MHz, and/or0.625 MHz channel width. During such downclocked operation, the numberof tones used by the transform module 304 or 404 may remain the same insome aspects.

Downclocking operation of the wireless device 202 may comprise operatingone or more of the components illustrated in FIG. 2 at a reduced clockrate. For example, the downclocking may comprise operating the processor204, the signal detector 218, the DSP 220, and/or any other digitalsignal circuitry at a lower rate, for example by adjusting, modifying,or assigning the timing settings of one or more of these components. Insome aspects, the downclocked operation is performed in response to acommand from the processor 204. In some aspects, the processor 204provides a clock signal which is reduced in comparison to a clock signalused when operating in the 20 MHz, 40 MHz, or 80 MHz channel width.

In some aspects, the processor 204 is configured to cause the operationof the wireless device 202 of FIG. 2 to be downclocked by a factor of 10(e.g., by 10×). In such configuration, operation in the 20 MHz channelwidth will be downclocked to operation in a 2 MHz channel width, andoperation in the 40 MHz channel width will be downclocked to operationin a 4 MHz channel width. Furthermore, operation in the 80 MHz channelwidth will be downclocked to operation in an 8 MHz channel width, andoperation in the 160 MHz channel width will be downclocked to operationin a 16 MHz channel width.

Similarly as described above, in one aspect, when a 1 MHz bandwidth fortransmission or reception of OFDM symbols is used, a 32 point transformmodule 304 or 404 may be used. In this case, tones may be allocated as24 data tones, 2 pilot tones, 5 guard tones, and a DC tone. In anotheraspect, when a 2 MHz bandwidth for transmission or reception of OFDMsymbols is used, a 61 point transform module 304 or 404 may be used. Inthis case, tones may be allocated as 52 data tones, 4 pilot tones, 7guard tones, and a DC tone. In yet another aspect, when a 4 MHzbandwidth for transmission or reception of OFDM symbols is used, a 64point transform module 304 or 404 of FIGS. 3 and 4 may be used. In thiscase tones may be allocated as 108 data tones, 6 pilot tones, 11 guardtones, and three DC tones. In yet a further aspect, when a 8 MHzbandwidth for transmission or reception of OFDM symbols is used, a 256point transform module 304 or 404 may be used. In this case tones may beallocated as 234 data tones, 8 pilot tones, 11 guard tones, and three DCtones. Accordingly, the spacing between tones for these bandwidths maybe 31.25 KHz. In addition, the symbol duration may be 40 us including acyclic prefix of either 4 μs (for short cyclic prefixes) or 8 μs (forlong cyclic prefixes). A longer cyclic prefix may be used to accommodateoutdoor delay spreads. Furthermore, large symbol durations may be neededto keep cyclic prefix overhead manageable.

In some aspects, the amount by which operation of the wireless device202 of FIG. 2 is downclocked is predetermined. For example, thedownclocking factor may be stored in the memory 206, and loaded atstartup of the wireless device 202. In such configuration, the processor204 may cause the wireless device 202 to operate in a downclocked modeaccording to the predetermined or loaded downclocking factor.

In some aspects, the amount by which operation of the wireless device202 of FIG. 2 is downclocked at any given time may be determined insitu. For example, the signal detector 218 may determine a downclockingfactor from a beacon or pilot received by the receiver 212. In someaspects, this factor is determined at startup of the device, or whenconnecting to the network for the first time. In some aspects, a newfactor is determined during handoff of the wireless device 202 or eachtime the wireless device 202 connects to a new network. In some aspects,a predetermined factor may be modified or updated based on a receivedsignal, such as based on a received beacon or pilot. In this way, thewireless device 202 may operate in different bandwidths pursuant to alocation of the device or a network to which the device is connecting,for example. The processor 204 may cause the wireless device 202 tooperate in a downclocked mode according to the determined downclockingfactor.

In some aspects, the wireless device 202 of FIG. 2 is permanentlyconfigured to operate in the downclocked mode. For example, thecomponents of the wireless device 202 may be hardwired or have firmwareinstalled therein that causes the device to always perform downclockedoperation. In such aspects, the wireless device 202 may be incapable ofcommunicating in the 20 MHz, 40 MHz, and 80 MHz channel widths. Further,the factor of downclocking may be fixed in such aspects. For example,the components may be manufactured and/or installed so as to implementonly the fixed downclocking factor. In other aspects, the wirelessdevice may be operated in any of the 20 MHz, 40 MHz, and 80 MHz channelwidths, or may be selectively downclocked by the processor 204 tooperate in the 1 MHz, 2 Wiz, 4, Wiz, 8 MHz, and 16 MHz channel width.

In some implementations, when transmitting in a sub-gigahertz range(e.g., 900 MHz), a repetition mode may be used where repetition codingis implemented. A repetition mode may allow for accurate transmissionover long distances without sacrificing too much preamble overhead. Insome implementations 2× repetition encoding may be used. For example,repetition encoding may allow for as little as 105 dB of pathloss toprovide good in-home coverage. When using a wireless sensor network,without repetition coding, customers may have to install higher-powersensors in difficult to reach places. It may not be practical to selltwo types of sensors (sensors for “easy to reach places” versus“difficult to reach places”). Furthermore, high-power sensors may not beable to work with low power batteries (e.g., coin-cell batteries) due topeak current drain. Alternatively, without repetition, multiple APscould be installed. However, choosing location and configuration of theAPs could be non-trivial for an average consumer. As such, repetitioncoding may provide various advantages for certain implementations forlow data rate applications such as sensor networks.

As an example, in one aspect BPSK rate ½ coding may be used with 4×repetition yielding 94 Kbps. In another aspect, BPSK rate ½ coding maybe used with 2× repetition yielding 188 Kbps. In yet another aspect,BPSK rate ½ coding may be used yielding 375 Kbps. In a further aspect,64 QAM rate ¾ coding may be used resulting in 3.75 Mbps.

In some implementations, the 1 MHz mode and the 2 MHz mode may berequired and configured to be interoperable. Using two required modesmay avoid issues where devices could be configured for some regulatoryregions but may not work for other regulatory regions and may allow fordevices to have more options if regulatory constraints change allowingfor less restrictive communications. Higher bandwidths (e.g., 8 MHz) maybe used for cellular offload.

With reference to FIG. 7, when transmitting packets in sub-gigahertzbands with bandwidths as described above, the preamble 702 may bedesigned to have robust mode detection in an early state of the preambleto detect between different modes. The preamble 702 may further beoptimized to minimize overhead and provide adequate coexistence ofdevices transmitting using the 1 MHz mode and devices transmitting usinggreater than or equal to 2 MHz modes. The preamble 702 may be designedto have robust mode detection in an early state of the preamble todetect between 1 MHz transmissions (32 pt FFT) and 2 MHz transmissions(64 pt FFT). The physical layer packet 700 may be generated fortransmission for different data rates to allow in one aspect fortransmission of data over greater distances. For example, the physicallayer packet 700 may be generated for a low data rate along with another“normal” data rate as described above.

FIG. 8A is a block diagram showing an example structure of a preamble802 a and payload 810 a of a physical layer packet 800 a fortransmission over a bandwidth of substantially 1 MHz according tocertain implementations. The physical layer packet 800 a may begenerated using a transform module 304 (FIG. 3) that is configuredaccording to a 32 point FFT mode for transmitting an OFDM symbol with 32tones as described above.

The preamble 802 a may include a short training field (STF) 804 a. TheSTF 804 a may include a sequence of known values with a subset ofnon-zero values corresponding to a subset of non-zero tones with aparticularly chosen periodicity. The periodicity of the non-zero tonesmay be the same as used for STF sequences used in higher bandwidths suchas 2 MHz. In some implementations, the STF field 804 a may be boosted,such as by 3 dB for repetition coding. The STF 804 a may be sent overfour OFDM symbols where each symbol repeats a known STF sequence.

The preamble 802 a may include a long training field (LTF) 806 a. TheLTF 806 a may be formed of four OFDM symbols and may include an LIEsequence transmitted in each symbol. The LTF sequences may be formed ofknown non-zero values corresponding to non-zero tones for all pilot anddata tones. In some implementations, the LTF sequences may thereforeinclude 26 non-zero values.

The preamble 802 a may include a signaling field (SIG) 808 a. In someimplementations, the SIG field 808 a may be repetition coded or 2×repetition coded. The physical layer packet 800 a may further includethe payload 810 a that may be generated using 24 tones in each OFDMsymbol allocated for data. The preamble 802 a may be used for generatingeither a low rate or a normal rate 1 MHz transmission. The preamble 802a may be used according to a single user mode.

As described above, the SIG field 808 a for a 1 MHz mode may be twosymbols. In one implementation, the entries into the SIG field 808 a maycorrespond to the entries shown in Table I below. As such, the SIG field808 a may include 36 bits. The SIG field 808 a may be coded at BPSK-rate½ repetition 2×.

TABLE 1 Field Bits Description Space Time 1 May indicate whether SpaceTime Block Coding Block Coding is used Number of Spatial 2 Streams ShortGuard Interval 1 Coding 2 1^(st) bit may be coding type (LDPC/BCC) while2^(nd) bit may be for LDPC N_(sym) ambiguity Modulation Coding 4 Scheme(MCS) Aggregation Bit 1 Signals use of AMPDU Length 9 My be in symbolswhen aggregation is on or in bytes when aggregation is off. An AMPDU maybe required for packet sizes greater than 511 bytes Reserved 6 May beused for MAC bits CRC 4 Tail 6 May be needed for BCC but could be lessbits

FIG. 8B is a block diagram showing an example structure of a preamble802 b and payload 810 b of a physical layer packet 800 b fortransmission over a bandwidth of substantially 2 MHz according to asingle user mode. The physical layer packet 800 b may be generated usinga transform module 304 (FIG. 3) that is configured according to a 64point FFT mode for transmitting an OFDM symbol with 64 tones asdescribed above.

The preamble 802 b may include a short training field (STF) 804 b. TheSTF 804 b may include a sequence of known values with a subset ofnon-zero values corresponding to a subset of non-zero tones over 64tones with a determined periodicity. The periodicity of the non-zerotones may be the same as used for STY sequences used for 1 MHztransmissions. The preamble 802 b may further include a long trainingfield (LTF) 806 b. The LTF 8061 may be formed of two OFDM symbols andmay include LTF sequences transmitted in each symbol. The LTF sequencesmay comprise non-zero values corresponding to non-zero tones for allpilot and data tones. The LTF sequences may therefore include 56non-zero values in some implementations. The preamble 8021 may furtherinclude a signaling field (SIG) 808 b. The SIG field 808 b may be formedfrom two OFDM symbols. The two OFDM symbols of the SIG field 808 h mayeach be QBPSK rotated. If more than one spatial streams are being used,the preamble 802 b may include additional long training fields (LTFs)816 b for each of the additional spatial streams being used (e.g., asthe LTF 804 b may correspond to the first spatial stream if there aremore than one). The physical layer packet 800 b may further include thepayload 810 b that may be generated using 52 tones in each OFDM symbolallocated for data. The preamble 802 b may be used according to a singleuser mode.

FIG. 8C is a block diagram showing an example structure of a preamble802 c and payload 810 c of a physical layer packet 800 c fortransmission over a bandwidth of 2 MHz according to a multi-user mode.As described above with reference to FIG. 8B, the physical layer packet800 c may be generated using a transform module 304 (FIG. 3) that isconfigured according to a 64 point HT mode for transmitting an OFDMsymbol with 64 tones.

The preamble 802 c may include a short training field (STF) 804 c. TheSTF 804 c may include a sequence of known values with a subset ofnon-zero values corresponding to a subset of non-zero tones over 64tones with a determined periodicity. The periodicity of the non-zerotones may be the same as used for STF sequences used for 1 MHztransmissions. The preamble 802 c may further include a long trainingfield (LTF) 806 c. The LTF 806 c may be formed of two OFDM symbols andmay include LTF sequences transmitted in each symbol. The LTF sequencesmay comprise non-zero values corresponding to non-zero tones for allpilot and data tones. The LTF sequences may therefore include 56non-zero values according to some implementations. The preamble 802 cmay further include a signaling field (SIG) 808 c. The SIG field 808 cmay be formed from two OFDM symbols. The first of the two OFDM symbolsof the SIG field 808 c may be QBPSK rotated. In one aspect, this allowsfor the receiver to detect whether the packet 800 c is multi-user modepacket or a single user mode packet based on whether only one of the SIGfield symbols is QBPSK rotated. The preamble 802 c may further include avery high throughput short training field (VHT-STF) 814 c. The VHT-STF814 c may correspond to a VHT-STF used for IEEE 802.11ac transmissions.The preamble 802 c may further include one or more very high throughputlong training fields (VHT-LTFs) 816 c corresponding to each spatialstream being used. The VHT-LTFs 816 c may correspond to VHT-LTFs usedfor IEEE 802.11ac transmissions. The preamble 802 c may further includea very high throughput signal field (VHT-SIG-B) 818 c. The VHT-SIG-B 818c may correspond to the VHT-SIG-B used for IEE 802.11ac transmissions.The physical layer packet 800 c may further include the payload 810 cthat may be generated using 52 tones in each OFDM symbol allocated fordata. The preamble 802 c may be used according to a multi-user mode.

Differentiating between a 32 point mode (i.e., 1 MHz) and a 64 pointmode (2 MHz) may be done by using an LTF sequence that is orthogonal infrequency across 32 and 64 tone mode, or by detecting the QBPSK rotationon the 1^(st) SIG symbol.

As described above, a wireless device 202 of FIG. 2 may be configured togenerate OFDM symbols for transmission over bandwidths greater than 2MHz, such as for 4 MHz, 8 MHz, 16 MHz, and 32 MHz. In someimplementations, when sending OFDM symbols over bandwidths greater than2 MHz, the SIG field 808 b (FIG. 8B) may be duplicated in every 2 MHzsegment of the OFDM symbol and may be used to be able to determine thebandwidth of the symbol. As the OFDM symbol for the SIG field may use 52tones allocated for data, duplication of the SIG field may leave 7 guardtones (3 and 4 tones on the ends of the symbol) for higher bandwidths (4MHz, 8 MHz, 16 MHz).

In some cases, it may be desirable to use additional guard tones for theLTF 806 b and/or SIG 808 b fields (FIG. 8B). For example, it may bedesirable for the 4 MHz, 8 MHz, and 16 MHz preamble symbols tocorrespond to corresponding symbols used for 40 MHz, 80 MHz, and 160 MHzof 802.11ac transmissions. As one example, the LTF 806 b may use theVHT-LTFs for 40 MHz, 80 MHz, and 160 MHz 802.11ac transmissionsdepending on whether the OFDM symbol is for 4 MHz, 8 MHz, and 16 MHzrespectively. As the VHT-LTFs for 40 MHz, 80 MHz, and 160 MHz have guardtones (5/6), using these VHF-LTFs may not provide non-zero values forchannel estimation for 2 tones at each edge, for example if the SIG 808b field allocated 52 tones for data. Furthermore, there may be stricterfiltering requirements for symbols being transmitted using greaterbandwidths (4 MHz, 8 MHz, and 16 MHz) if the LTF 806 b and SIG 808 b aretransmitted using 52 data tones (i.e., having less guard tones).Duplicating the LTF 806 b used for 2 MHz transmissions may inadequatelyaddress these issues as the LTF uses 52 non-zero tones, and thus thesame guard tone issue remains. As such, an optimized LIE 806 b and SIG808 b may be provided for 2, 4, and 8 MHz transmissions. In one aspect,the fields are chosen so as to be able to re-use 20, 40, and 80 MHz LTFsequences used for IEEE 802.11ac packets.

As such, in one implementation, for the 2 MHz packets shown in FIGS. 8Band 8C, the SIG fields 808 b and 808 c may be transmitted using adifferent tone allocation than the rest of the fields of the packets 800b and 800 c. For example, The SIG fields 808 b and 808 c may betransmitted using 48 data tones rather than 52 data tones. This maycorrespond to the tone allocation used for an L-SIG of 802.11a toneallocation. This SIG field 808 b and 808 c may then be duplicated foreach 2 MHz segment for transmissions over 2 MHz. In anotherimplementation, the STFs 804 b and 804 c, the LTFs 806 b and 806 c, andthe SIG fields 808 b and 808 c may be generated for transmission using adifferent tone allocation than the rest of the fields of the packet. Forexample the STFs 804 b and 804 c, the LTFs 806 b and 806 c, and the SIGfields 808 b and 808 c may be generated for transmission using 48 tonesallocated for data.

As described above, the SIG fields 808 h and 808 c for a 2 MHz mode mayuse two symbols transmitting up to 52 bits of data. The entries into theSIG fields 808 b and 808 c may correspond to the entries shown in Table2 below. The first 26 bits that are un-shaded may correspond to thefirst symbol while the last 26 bits that are shaded may correspond tothe second symbol. It should be appreciated that while 52 bits of dataare shown in the table below, however as described above, in someimplementations, the SIG fields 808 b and 808 c may be sent using 48data tones and as such the SIG field may correspond to 48 bits. In onecorresponding implementation, the number of reserved bits shown in Table2 below may be reduced so that 48 bits are sent or received.

TABLE 2

FIG. 9 illustrates an example format of a packet 900. The packet 900 maycomprise a PPDU for use in the wireless communication system 100 ofFIG. 1. In some aspects, the packet 900 is used when the wireless device202 (FIG. 2) is operating in a basic mode. In some aspects, the packet900 is referred to as a basic packet. The packet 900 may be used forsensors, and may support operation in one or two bandwidths, forexample, the two lowest bandwidths used according to the 802.11ahstandard.

The packet 900 includes a preamble 910 and a payload 920. The preamble910 includes a short training field (STF) 912, a long training field(LTF) 914, and a signal (SIG) field 916. In the aspect illustrated inFIG. 9, the SIG field 916 is referred to as an Omni-SIG. The payload 920may include user information or data and directly follow the SIG field916, as in the aspect illustrated in FIG. 9.

The STF 912 may comprise one or more sequences. In some aspects, thesequence in the STF 912 is repeated a plurality of times. The STF 912may be used by the receiver 212 of the wireless device 202 (FIG. 2) toset or adjust a gain of a receive amplifier. For example, automatic gaincontrol may be performed to set a gain of a LNA. Further, the receiver212 or the wireless device 202 may use the STF 912 to detect a beginningof the packet 900. As shown, the STF 912 may comprise 2 symbols.

The LTF 914 may also comprise one or more sequences. The LTF 914 may beused by the processor 204, the signal detector 218, or the DSP 220 ofthe wireless device 202 (FIG. 2) to estimate a channel over which thepacket 900 is received and/or to equalize symbols received in thepayload 920. As shown, the LTF 914 may comprise one or two symbols.

The SIG field 916 may comprise information regarding parameters of thepacket 900 and the payload 920. For example, the SIG field 916 mayindicate a length of the packet 900 or a modulation coding scheme (MCS)of the payload 920. As shown, the SIG field 916 may comprise one or twosymbols. The contents and format of the SIG field 916 are described inadditional detail in this disclosure.

FIG. 10 illustrates an example format of a packet 1000. The packet 1000may comprise a PPDU for use in the wireless communication system 100 ofFIG. 1. In some aspects, the packet 1000 is used when the wirelessdevice 202 (FIG. 2) is operating in an advanced mode. In some aspects,the packet 1000 is referred to as an advanced packet. The packet 1000may be implemented for non-sensor uses and/or for uses that require morethan two bandwidths. As will be discussed further below, the packet 1000may support multi-user multiple input multiple output (MU-MIMO)communications.

The packet 1000 includes a preamble 1010 and a payload 1020. Thepreamble 1010 includes the STF 912, the LTF 914, and the SIG field 916illustrated in FIG. 9. In contrast to the preamble 910, however, thepreamble 1010 further includes an extension field 1012. In FIG. 10, theextension field 1012 is illustrated as an extension SIG field. In someaspects, the SIG field 916 indicates whether the extension field 1012 isincluded in a packet. Thus, the SIG field 916 may be used to distinguishbetween a basic packet and an advanced packet in some aspects. Thepayload 1020 may include user information or data, and may be configuredsimilar to the payload 920. In some aspects, the payload 1020 may belonger than the payload 920.

The extension SIG field 1012 may comprise parameters of the packet 1000or the payload 1020 in addition to the parameters included in the SIGfield 916. In some aspects, the extension SIG field 1012 includesinformation that is not included in the SIG field 916. In some aspects,the extension SIG field 1012 includes information relating to theparameters in the SIG field 916, which information may be used tosupplement the SIG field 916. The extension SIG field 1012 may compriseone or two symbols, and may be disposed between the SIG field 916 andthe payload 1020. The contents and format of the extension SIG field1012 are described in additional detail in this disclosure.

FIG. 11 illustrates an example format of a packet 1100. The packet 1100may comprise a PPDU for use in the wireless communication system 100 ofFIG. 1. In some aspects, the packet 1100 is used when the wirelessdevice 202 (FIG. 2) is operating in an extended range (XR) mode. In someaspects, the packet 1100 is referred to as an extended range or XRpacket. The packet 1100 may provide a robust preamble and data encodingso as to increase the range over which the packet 1100 may be correctlyreceived and decoded.

The packet 1100 includes a preamble 1110 and a payload 1120. Thepreamble 1110 includes a short training field (STF) 1112, a longtraining field (LTF) 1114, and a signal (SIG) field 1116. In the aspectillustrated in FIG. 11, the SIG field 1116 is referred to as anOmni-SIG. The payload 1120 may include user information or data, and maybe configured similar to the payload 920 or 1020. In some aspects, thepayload 1120 may be shorter than the payload 920 or 1020.

Similar to the STF 912, the STF 1112 may comprise one or more sequences.The sequence included in the STF 1112, however, may be repeated agreater number of times than the sequence in the STF 912. The STF 912may be used to set or adjust a gain of a receive amplifier or to detecta beginning of the packet 900. As shown, the STF 1112 may be longer thanthe STF 912. For example, the STF 1112 may comprise 3 symbols.

The format of the STF 1112 may be formatted in any number of ways. Inone aspect, the format of the STF 1112 may be based on a Chui sequence.In some aspects, the format may be based on a quantum-dot cellularautomata (QCA) design, for example by populating every tone with a 32point fast Fourier transform (FFT). In other aspects, every other tonemay be populated by a 64 point FFT.

The LTF 1114 may also comprise one or more sequences. The LTF 1111 maybe used to estimate a channel over which the packet 1100 is received,and/or to equalize symbols received in the payload 1120. As shown, theLTF 1114 may be longer than the LTF 914. For example, the LTF 1114 maycomprise two or more symbols. In some aspects, one of the symbols of theLTF 1111 is flipped when compared to a respective symbol in the LTF 914.The LTF 1114 may be repeated a plurality of times in some aspects.

The SIG field 1116 may comprise information regarding parameters of thepacket 1100 and the payload 1120. For example, the SIG field 1116 mayindicate a length of the packet 1100 or a modulation coding scheme (MCS)of the payload 1120. The SIG field 1116 may comprise two or moresymbols. In some aspects, a plurality of bits representing sub-field ofthe SIG field 1116 are repeated four or more times in the SIG field1116. For example, the SIG field 1116 may be represented by 19 bits, aswill be discussed in further detail below, which bits may be repeatedfour times to occupy three symbols. In some aspects, the SIG field 1116is modulated using a form of binary phase-shift keying (BPSK) such asBPSK ½. In some aspects, a different coding may be used instead ofrepetition of the bits or instead of using a binary convolutional code(BCC), which may reduce the length of the SIG field 1116, for example totwo symbols. The different coding may include a block code. The contentsand format of the SIG field 1116 are described in additional detail inthis disclosure.

The wireless device 202 t may be configured to determine which of thepackets discussed in this disclosure to transmit. This determination maybe based on any number of factors. For example, network congestion maybe considered, as may the type or amount of data being transmitted.

In some aspects, the processor 204 of the wireless device 202 (FIG. 2)determines to transmit the packet 1000 instead of the packet 900 whenMU-MIMO is used, when the length of the packet will be greater than athreshold amount, when a default mode is not being used for data, whenthe wireless device 202 is not operating at one of two lowestbandwidths, or when the forward error correction (FEC) being used is notBCC. In some aspects, the threshold amount is approximately 4096 bytes.In some aspects, the default mode relates to whether a short guardinterval (SGI) or long guard interval (LGI) is being used.

The processor 204 of the wireless device 202, (FIG. 2) may furthergenerate a packet, indicating whether the packet is formatted as thepacket 900 or the packet 1000 with the SIG field 916. In some aspects,the wireless device 202 may rotate a modulation, such as the BPSK, ofthe SIG field 916 to indicate the type of the packet. In some aspects, abit or other indicator may be transmitted over a quadrature phase (e.g.on the Q rail) during one of the symbols of the SIG field 916 toindicate whether the packet 900 or 1000 is being transmitted.

The processor 204 of the wireless device 202 (FIG. 2) may determine aformatting of a received packet based on the SIG field 916 and processthe payload accordingly. For example, when the extension field 1012 isincluded in the preamble 1010, the wireless device 202 may decode orotherwise process the payload 1020 using parameters in the extensionfield 1012 such as an MCS or number of spatial streams. In some aspects,the wireless device 202 may be configured to decode packets having oneof the formats 900 and 1000, and to ignore packets having the otherformat. For example, some devices may not implement multi-user (MU)functionality which utilizes information in the extension field 1012. Ifthese devices determine that the extension field 1012 is included basedon the SIG field 916, the processor 204 may cease further processing ofthe packet 1000 or abort receiving any further portion of the packet1000. In this way, the device may identify packets that are not intendedfor the device, and may save power by aborting reception of thosepackets.

FIG. 12 illustrates an example 916 a of the SIG field 916. The SIG field916 a may be used with the aspects described in this disclosure wherethe type of packet is indicated using a rotated BPSK or Q-rail bit, forexample. The SIG field 916 a, comprises a length sub-field 1202including 12 bits, an MCS sub-field 1204 including 4 bits, a bandwidth(BW) sub-field 1206 including 1 bit, a parity sub-field 1208 including 1bit, a reserved sub-field 1212 including 2 bits, and a tail sub-field1214 including 6 bits. The length sub-field 1202 may indicate a lengthof the packet 900 or 1000 in bytes. The MCS sub-field 1204 may indicatean MCS used for the payload 920, 1020. The bandwidth sub-field 1206 mayindicate which bandwidth is being used. In the illustrated aspect, theSIG field 916 a comprises one symbol.

In some aspects, a format of the packet generated by the processor 204(FIG. 2) may be indicated by one or more sub-fields or hits in the SIGfield 916. For example, when generating the packet, the processor 204 ofthe wireless device 202 (FIG. 2) may include an explicit indicator inthe SIG field 916 to distinguish the packet 900 from the packet 1000.When another wireless device 202 receives the packet, the processor 204of the wireless device 202 may determine a formatting of the packetbased on a subfield of the SIG field 916 and process the payloadaccordingly.

In one aspect, the inclusion of the extension field 1012 is determinedusing a mode sub-field of the SIG field 916. The mode sub-field maycomprise two bits and may be used to indicate a number of spatialstreams or a number of bandwidth portions used for the packet. In someaspects, the packet 900 is utilized when the payload 920 is transmittedover one spatial stream. In some aspects, the packet 1000 is utilizedwhen the payload 1020 is transmitted over more than one spatial stream.For example, the extension sub-field 1012 may be included when singleuser MIMO (SU-MIMO) or MU-MIMO is used. The mode sub-field is describedin additional detail below.

FIG. 13A illustrates an example 916 b of the SIG field 916. The SIGfield 916 b may be used in the packet 900 with the aspects described inthis disclosure where the type of the packet is indicated using asubfield of the SIG field 916 b, for example. The SIG field 916 bcomprises the length sub-field 1202, the MCS sub-field 1204, a modesub-field 1302 as discussed above, a SGI sub-field 1304 including 1 bit,the parity sub-field 1208, and the tail sub-field 1214. In the aspectillustrated in FIG. 13A, the length sub-field 1202 may indicate a lengthof the packet 900 in bytes or symbols. The parity sub-field 1208 mayonly apply to the mode sub-field 1302 and the SGI sub-field 1304 in someaspects. In the illustrated aspect, the SIG field 916 b comprises onesymbol.

The following table illustrates example values of the mode sub-field1302. The table further enumerates a number of spatial streams andbandwidths that may be used for each of the values of the mode sub-field1302, and the table further describes whether the length of the packet900 is described in the bytes or symbols in the length sub-field 1202.

TABLE 3 Mode “00” Basic BW, 1 ss Length in bytes “01” BW X 2, 1 ssLength in symbols “10” BW X 4, 1 ss Length in symbols “11” Ext SIG ExtSIG present

As can be seen from the table above, the length may be indicated insymbols when more than one bandwidth is used. In some aspects, anaggregate MAC protocol data unit (A-MPDU) is used when more than onebandwidth is used, the length of which may be sufficiently indicated insymbols. As can also be seen above, the extension field 1012 may beincluded when the mode sub-field 1302 is set to “1 1.” Thus, the SIGfield 916 b may be used when the mode sub-field 1302 is set to “0 0,” “01.” or “1 0.”

FIG. 13B illustrates an example 916 c of the SIG field 916. The SIGfield 916 c may be used in the packet 1000 with the mode sub-field 1302described above. Thus, the SIG field 916 c may be used when the modesub-field 1302 is set to “1 1” and the extension field 1012 is included.The SIG field 916 c comprises a length sub-field 1312, a bandwidthsub-field 1314, a reserved sub-field 1316 including 4 bits, the modesub-field 1302 as discussed above, the parity sub-field 1208, the SGIsub-field 1304, and the tail sub-field 1214. In the aspect illustratedin FIG. 13B, the length sub-field 1312 may indicate a length of thepacket 1000 in symbols. In contrast to the length sub-field 1202,however, the length sub-field 1312 includes 10 bits. The bandwidthsub-field 1314 may indicate a number of bandwidths being used and mayinclude 2 bits. In the illustrated aspect, the SIG field 916 c comprisesone symbol.

FIG. 14 illustrates an example 916 d of the SIG field 916. The SIG field916 d may be used with the aspects described in this disclosure wherethe type of packet is indicated using a subfield of the SIG field 916 d.For example, the inclusion of the extension field 1012 may be indicatedby an MU-extension sub-field 1414. In the aspect illustrated in FIG. 14,the MU-extension sub-field 1414 includes one bit, may be set to “0” toindicate that the extension field 1012 is not included, and may be setto “1” to indicate that the extension field 1012 is included. In someaspects, the extension field 1012 comprises a SIG field and is includedfor MU transmissions. In such aspects, the extension field 1012 may bereferred to as an MU-SIG. In the illustrated aspect, the SIG field 916 dcomprises two symbols.

The SIC field 916 d comprises a rate sub-field 1402 including 4 bits, aspatial streams sub-field 1404, the short guard interval (SGI) sub-field1304, a length sub-field 1406 including 18 bits, acyclic redundancycheck (CRC) sub-field 1408 including 4 bits, the tail sub-field 1214, abandwidth sub-field 1412, the MU-extension sub-field 1414, anaggregation sub-field 1416 including 1 bit, and a reserved sub-field1418. When the SIG field 916 d is used for SU, the length sub-field 1406may indicate a length of the packet 900 in bytes or octets. This allowsthe PHY layer to determine the boundary of the packet 900 when an A-MPDUis not used. When the SIC field 916 d is used for MU, however, thelength sub-field 1406 may indicate a maximum length of the packet 1000among users in symbols. In this situation, an A-MPDU may be used withtransmission of the packet 1000. Similar to the bandwidth sub-field1314, the bandwidth sub-field 1412 may be used to indicate a number ofbandwidths or modes being used, except that the bandwidth sub-field 1412may include 2 or 3 bits.

In some aspects, the rate sub-field 1402 may indicate the MCS of thepayload 920. The spatial streams sub-field 1404 may indicate a number ofspatial streams for SU operation and/or number of spatial streamsreserved for MU operation. The length sub-field may indicate the lengthof the packet 900 in octets if the MU extension sub-field 1414 is 0 andindicate length in symbols if the MU extension sub-field 1414 is 1. Theaggregation sub-field 1416 may be reserved if the MU extension sub-field1414 is 1 and may indicate the packet 900 is an A-MPDU if the MUextension sub-field 1414 is 0.

FIG. 15 illustrates an example 1012 a of the extension field 1012. Inthe illustrated aspect, the extension field 1012 a comprises a twosymbol extension SIG field. The extension SIG field 1012 a comprises anMCS sub-field 1502 including 16 bits, a length sub-field 1504 including4 bits, a bandwidth sub-field 1506 including 1 bit, an SGI/LGI sub-field1508 including 1 bit, a coding sub-field 1512 including 4 bits, aspatial streams sub-field 1514 including 8 bits, a group ID (GID)sub-field 1516 including 6 bits, a CRC sub-field 1518 including 4 bits,a reserved sub-field 1522 including 2 bits, and a tail sub-field 1524including 6 bits.

The MCS sub-field 1502 may indicate an MCS for each of a plurality ofusers. In the illustrated embodiment, there may be up to four users. Thelength sub-field 1504 may indicate a length of the packet 1000 insymbols. The bandwidth sub-field 1506 may indicate a bandwidth used forthe packet 1000. The SGI/LGI sub-field 1508 may indicate whether an SGIor LGI is used. The coding sub-field 1512 may indicate a coding for eachof a plurality of users. In the illustrated embodiment, there may be upto four users. The spatial streams sub-field 1514 may indicate a numberof spatial streams for each of a plurality of users. In the illustratedembodiment, there may be up to four users.

In some aspects, any of the MCS sub-field 1502, the length sub-field1504, the bandwidth sub-field 1506, and the SGI/LGI sub-field 1508 mayindicate a parameter of the packet 1000 rather than a correspondingsub-field in the SIG field 916 indicating that parameter. For example,when the extension field 1012 a is included, the wireless device 202 rmay use the MCS sub-field 1502 to determine an MCS for one or more usersinstead of using the MCS sub-field 1204. In other aspects, one or moresub-fields in the SIG field 916 may indicate parameters for a firstuser, while any of the MCS sub-field 1502, the length sub-field 1504,the bandwidth sub-field 1506, and the SGI/LGI sub-field 1508 mayindicate parameters for one or more other users.

In some aspects, the length of the packet 1000 is indicated by acombination of the bits in the length sub-field 1504 with the bits in alength sub-field of the SIG field 916. For example, the length sub-field1312 may be set to the value “0000000010” and the length sub-field 1504may be set to the value “1111” to indicate that a length of the packet1000 is 47 symbols. Similarly, the number of bandwidths used for thepacket 1000 may be indicated by a combination of the bit in thebandwidth sub-field 1506 with the bits of a bandwidth sub-field in theSIG field 916.

FIG. 16 illustrates an example 1012 b of the extension field 1012. Inthe illustrated aspect, the extension field 1012 b comprises a twosymbol extension SIG field. The extension SIG field 1012 b comprises theMCS sub-field 1502, the spatial streams sub-field 1514, the GIDsub-field 1516, the CRC sub-field 1518, a reserved sub-field 1602including 10 bits, and the tail sub-field 1524. As can be seen in FIG.16, the extension SIG field 1012 b is formatted similar to the extensionSIG field 1012 a, except that the sub-fields 1504-1512 are omitted inthe extension SIG field 1012 b, and the reserved sub-field 1602 includesa greater number of bits than the reserved sub-field 1522.

FIG. 17 illustrates an example format of a packet 1700. The packet 1700may comprise a PPDU for use in the wireless communication system 100 ofFIG. 1. In some aspects, the packet 1700 is used when the wirelessdevice 202 (FIG. 2) is operating in the advanced mode, and the packet1700 may be referred to as an advanced packet.

The packet 1700 includes a plurality of extension fields 1732-1738 in apreamble 1710 of the packet 1700. The extension fields may include anMU-SIG field 1732, a precoded STF 1734, one or more LTFs 1736, and aSIG-B field 1738. In some aspects, the packet 1700 may be used insteadof the packet 1000.

In addition to the extension fields 1732-1738, the preamble 1710includes a high throughput (HT) STF 1712, an HT-LTF1 1714, and thesignal (SIG) field 916. In the aspect illustrated in FIG. 9, the SIGfield 916 is referred to as an Omni-SIG. In some aspects, the SIG field916 indicates whether the extension fields 1732-1738 are included in apacket. For example, one or more bits in the SIG field 916, a BPSKrotation of the SIG field 916, and/or a bit on the Q-rail during asymbol of the SIG field 916 may indicate that the extension fields1732-1738 are included.

The HT-STF 1712 may comprise one or more sequences. In some aspects, thesequence in the STF 1712 is repeated a plurality of times. The HT-STF1712 may be used by the receiver 212 of the wireless device 202 (FIG. 2)to set or adjust a gain of a receive amplifier or used to detect abeginning of the packet 1700. As shown, the HT-STF 1712 may comprise 2symbols.

The FIT-LTF 1714 may also comprise one or more sequences. The HT-LTF1714 may be used by the processor 204, the signal detector 218, or theDSP 220 of the wireless device 202 (FIG. 2) to estimate a channel overwhich the packet 1700 is received and/or to equalize symbols received ina payload 1720. As shown, the HT-LTF 1714 may comprise two symbols.

In some aspects, the MU-SIG field 1732 includes one or more of thesub-fields illustrated in FIGS. 15 and 16. In some aspects, the MU-SIGfield 1732 and the SIG-B field 1738 are collapsed together to create atwo symbol field. When the MU-SIG field 1732 and the SIG-B field 1738are collapsed, the combined contents may include a GID sub-field, anN_(sts) (number of space time streams) sub-field, and/or an MCSsub-field. In some aspects, the MCS sub-field includes an MCS for eachuser. In some aspects, one or more of the SIG fields illustrated in FIG.17 can be used as an additional LTF.

As alluded to above, the packet 1700 may further include the payload1720. The payload 1720 may include user information or data, and may beconfigured similar to the payload 920.

FIG. 18 illustrates an example generalized format of a packet 1841 whichmay be used within the wireless communication system 100 of FIG. 1. Thepacket 1841 may comprise a PPDU, and may be selectively formattedaccording to either the basic mode or advanced mode described above. Insome aspects, the packet 1841 may be formatted according to a pluralityof other modes.

The packet 1841 includes a preamble 1851 and a payload 1861. Thepreamble 1851 includes the HT-STF 1712, the HT-LTF 1714, and the SIGfield 916. In some modes or formats, the packet 1841 may additionallyinclude an extension 1853.

The HT-STF 1712 and the HT-LTF 1714 allow for data transmission on 52tones. The extension 1853 may include one or more optional or extensionfields. The SIG field 916 may be used to indicate whether the extension1853 is included in the preamble 1851 and, when the extension 1853 isincluded, to indicate whether certain fields are included in theextension 1853. For example, for sensor transmissions using one spatialstream, the SIG field 916 may indicate that the extension 1853 isomitted and the SIG field 916 may be directly followed by the payload1861. The payload 1861 may include SU data or MU data, and/or aggregatedor non-aggregated MPDU information, for example, and may be configuredsimilar to the payloads discussed in this disclosure.

In some aspects, the STF 912 discussed above with respect to FIG. 9 maybe configured similar to the HT-STF 1712. Further, the LTF 914 discussedabove with respect to FIG. 9 may be configured similar to the HT-LTF1714.

The SIG field 916 is labeled as a SIG-A field in FIG. 18. In someaspects, the SIG-A field 916 may be configured similar to the Omni-SIGfields illustrated or discussed in this disclosure. In other aspects,the SIG-A field 916 may differ in configuration from the Omni-SIG fieldsillustrated or discussed in this disclosure. For example, the SIG-Afield 916 may be configured as discussed with respect to FIGS. 20 and23.

The packets discussed above may be formatted pursuant to the generalizedformat of the packet 1841. For example, when the extension 1853 isomitted, the packet 900 may be formatted similar to the packet 1841. Asanother example, when the extension 1853 is included, the packet 1000may be formatted similar to the packet 1841. In this example, theextension field 1012 may be included in the extension 1853. Similarly,when the extension 1853 is included, the packet 1700 may be formattedsimilar to the packet 1841. In this example, one or more of theplurality of extension fields 1732-1738 may be included in the extension1853.

The packet 1841 may be formatted to reduce overhead for devices that donot support or are not using MU-MIMO, for example, by omitting one ormore fields from the extension 1853 or by omitting the extension 1853altogether. Similarly, the extension 1853 or one or more fields of theextension may be omitted for devices that do not support or are notusing SU transmit beamforming (Tx-BF). Thus, sensors and other suchdevices may utilize non-AMPDU transmissions. Therefore, the packet 1841,and the implementations of the packet 1841 described below, support bothMU-MIMO and Tx-BF as optional features with little or no additionaloverhead for devices that do not support such features.

FIGS. 19A and 19B illustrate a first implementation showing a pluralityof formats that may be used for the packet 1841 discussed above. Each ofthe formats illustrated in FIGS. 19A and 19B include the HT-STF 1712,the HT-LTF 1714, and an example 916 e of the SIG field 916. The SIG-Afield 916 e may include two symbols.

FIG. 19A illustrates an example packet format 1941 of the packet 1841according to the first implementation, and FIG. 19B illustrates anexample packet format 1961 of the packet 1841 according to the firstimplementation. The wireless device 202 (FIG. 2) may distinguish betweenthe packet 1941 and the packet 1961 based on the SIG-A field 916 e, forexample.

With reference to FIG. 19A, the packet 1941 includes a preamble 1951 andthe payload 1861. The preamble 1951 includes the HT-STF 1712, the HT-LTF1714, and the SIG-A field 916 e discussed above. The preamble 1951optionally includes one or more additional LTFs 1953.

In some aspects, the packet 1941 is used for SU open loop transmission.In such aspects, the additional LTFs 1953 are omitted when one spatialstream is used for the packet 1941. When additional spatial streams areused, an additional LTF 1953 for each additional spatial stream may beincluded in the preamble 1951. In some aspects, 1, 2, or 4 spatialstreams may be used. In these aspects, 0, 1, or 2 additional LTFs 1953will be included in the preamble 1951.

In some aspects, an indicator in the SIG-A 916 e signifies whether theadditional LTFs 1953 are included. An example of such an indicator isdescribed with respect to FIG. 20.

With reference to FIG. 19B, the packet 1961 includes a preamble 1971 andthe payload 1861. The preamble 1971 includes the HT-STF 1712, theFIT-LTF 1714, and the SIG-A field 916 e discussed above. The preamble1971 further includes a precoded STF 1973 comprising one symbol, and aSIG field comprising one symbol. The precoded STF 1973 may be used inautomatic gain control (AGC) process. In FIG. 19B, the SIG field isillustrated as a SIG-B field 1977. The preamble 1971 optionally includesone or more precoded LTFs 1975. The precoded LTFs 1975 may be used tofor training purposes, for example, to estimate the channel over whichthe packet 1961 is received. Precoding may allow additional amounts ofdata to be transmitted per symbol. In some aspects, the SIG-B field 1977is precoded.

In some aspects, the packet 1961 is used for MU-MIMO or Tx-BFtransmission. Indicators in the SIG-A field 916 e may be used todifferentiate between such transmissions as will be discussed inadditional detail below. In some aspects, the precoded LTFs 1975 areincluded when more than one spatial stream is used, similar to how theadditional LTFs 1953 are included in the packet 1941 when more than onespatial stream is used. The inclusion or omission of the precoded LTFs1975 may be indicated in the same way as the inclusion or omission ofthe additional LTFs 1953.

In some aspects, a modulation of at least one of the symbols of theSIG-A field 916 e is used to identify whether the packet 1941 or thepacket 1961 is being transmitted. For example, the wireless device 202 tmay transmit the first symbol of the SIG-A field 916 e using a rotatedBPSK. When the wireless device 202 r receives the SIG-A field 916 e, thewireless device 202 r may determine that the packet 1961 is beingreceived. In some aspects, a QBPSK rotation is used. Thus, a rotation ofa symbol in the SIG-A field 916 e may indicate that the pre-coded STF1973 follows the SIG-A field 916 e, as well as indicating that the SIG-Bfield 1977 is included in the preamble 1971.

In some uses of the wireless communication system 100 of FIG. 1, SU openloop transmissions will be used with a greater frequency than eitherMU-MIMO or Tx-BF transmissions. For example, certain sensors configuredfor 802.11ah transmission may use SU open loop transmission. Thus, inthe first implementation, the packet 1941 may be used more often thanthe packet 1961, and the SIG-B field 1977 therefore omitted from manycommunicated packets.

FIG. 20 illustrates an example of the SIC-A field 916 e. The SIC-A field916 e includes an MCS sub-field 2051 comprising 4 bits, a spatialstreams sub-field 2053 comprising 2 bits, an SCI sub-field 2055comprising 1 bit, a length sub-field 2057 comprising 12 bits, abandwidth sub-field 2059 comprising 2 bits, an aggregation sub-field2061 comprising 1 bit, a coding sub-field 2063 comprising 1 bit, an MUsub-field 2065 comprising 1 bit, a space-time block code (STBC)sub-field 2067 comprising 1 bit, an AID/GID sub-field 2069 comprising 16bits, a reserved sub-field 2071 comprising 1 bit, a CRC sub-field 2073comprising 4 bits, and a tail sub-field 2075 comprising 6 bits.

The MCS sub-field 2051 indicates an MCS used when the SIG-A field 916 eis used in a SU transmission. The MCS sub-field 2051 is reserved for MUtransmission because the MCS for an MU transmission may be indicated inthe SIG-B field 1977. In some aspects, the SU transmission may beindicated by the symbols of the SIG-A field 916 e being transmittedwithout a rotated modulation, or by the MU sub-field 2065 being set tozero when a symbol of the SIG-A field 916 e is transmitted with arotated modulation.

The spatial streams sub-field 2053 may indicate the number of spatialstreams used in a SU transmission. When the spatial streams sub-field2053 indicates that more than one spatial stream is used, the additionalLTFs 1953 or precoded LTFs 1975 may be included. Thus, a value of thespatial streams sub-field 2053 may indicate whether one or more LTFs areincluded after the SIC-A field 916 e, as well as how many of theadditional LTFs are included. The spatial streams sub-field 2053 may bereserved for MU transmissions.

The length sub-field 2057 may indicate a length of the packet, or of thepayload of the packet, in which the SIG-A field 916 e is included. Thelength sub-field 2057 may indicate the length of the packet in byteswhen a non-aggregated MPDU is used with SU transmission. This ensuresthat the PHY layer of the wireless device 202 r may properly determinethe length of the packet. If MU is used or if A-MPDU is used, the lengthsub-field 2057 indicates the length of the packet in symbols. In someaspects, A-MPDU is always used for MU transmission. In some aspects.A-MPDU is always used for packets having a length that is greater than4095 bytes. When the length sub-field 2057 indicates the length insymbols, the length of the packet may be accurately determined becausedelimiters within the A-MPDU may carry an exact byte length. Further,the bandwidth sub-field 2059 may indicate a bandwidth used for thepacket 1941 or the 1961, for example.

The aggregation sub-field 2061 indicates whether MPDUs are beingaggregated when SU transmission is used. Thus, the aggregation sub-fieldindicates whether an A-MPDU is used, as well as indicates whether thelength sub-field 2057 should be interpreted as bytes or symbols. Theaggregation sub-field 2061 may be reserved for MU transmissions in someaspects.

The coding sub-field 2063 may indicate a coding for a plurality ofusers. The coding sub-field 2063 may indicate a coding type for SU, andmay be reserved in the case of MU.

As alluded to above, the MU sub-field 2065 indicates whether the SIG-Afield 916 e is included an MU transmission or an SU transmission. In theillustrated aspect, a value of “1” in the MU sub-field 2065 indicatesthat MU is being used, while a value of zero indicates that SU is beingused.

The STBC sub-field 2067 indicates STBC for some or all spatial streams.Further, the STBC sub-field 2067 may be used as in the 802.11acstandard.

The AID/GID sub-field 2069 will carry different information depending onwhether MU or SU is being used. When MU transmissions are not beingused, the AID/GID sub-field 2069 may indicate an association identifier(AID) of the device to which the packet carrying the SIG-A field 916 eis directed. When MU transmission are being used, the AID/GID sub-field2069 may indicate a group identifier (GID) of the devices to which thepacket carrying the SIG-A field 916 e is directed, as well as a numberof spatial streams being used. When the AID/GID sub-field 2069 indicatesthat more than one spatial stream is used, the precoded LTFs 1975 may beincluded. Thus, a value of the AID/CAD sub-field 2069 may indicatewhether one or more precoded LTFs 1975 are included after the SIG-Afield 916 e, as well as how many of the precoded LTFs 1975 are included.

FIG. 21 illustrates an example 1977 a of the SIC-B field 1977. The SIC-Bfield 1977 a includes an MCS sub-field 2151 comprising 4 bits, a codingsub-field 2153 comprising 1 bit, a reserved sub-field 2155 comprising 11bits, a CRC sub-field 2157 comprising 4 bits, and a tail sub-field 2159comprising 6 bits. In some aspects, a SIG-B field 1977 a is included foreach user transmission. Thus, each of the sub-fields 215 1-2159 mayinclude information for one user.

In some aspects, the SIG-B field 1977 may be omitted for SU Tx-BFtransmissions. This aspect, however, may involve an additional mode toproperly receive a packet omitting the SIG-B field. Thus, rather than awireless device implementing two modes, for example, the wireless devicemay implement three modes.

The first implementation discussed above with respect to FIG. 19provides support for SU-MIMO, STBC, short GI, AID-based power save, andbandwidths using only the SIG-A field. The preamble for suchcommunications may comprise only six symbols. Additional information maybe included for MU-MIMO or Tx-BF in an extension field, for example, aSIG-B field or one or more additional LTFs.

FIGS. 22A, 22B, and 22C illustrate a second implementation showing aplurality of formats that may be used for the packet 1841 discussedabove. Each of the formats illustrated in FIGS. 22A, 22B, and 22Cincludes the HT-STF 1712, the HT-LTF 1714, and an example 916 f of theSIG field 916. The SIG-A field 916 f includes one symbol.

FIG. 22A illustrates an example 2241 of a format of the packet 1841according to the second implementation, FIG. 22B illustrates an example2261 of another format of the packet 1841 according to the secondimplementation, and FIG. 22C illustrates an example 2281 of yet anotherformat of the packet 1841 according to the second implementation. Thewireless device 202 r may distinguish between the packets 2241, 2261 and2281 based on at least the SIG-A field 916 f.

With reference to FIG. 22A, the packet 2241 includes a preamble 2251 andthe payload 1861. The preamble 2251 includes the HT-STF 1712, the HT-LTF1714, and the SIG-A field 916 f discussed above. In some aspects, thepacket 2241 is used for open loop transmissions over one spatial stream.For example, certain sensors configured for 802.11ah transmission mayutilize the packet 2241.

With reference to FIG. 22B, the packet 2261 includes a preamble 2271 andthe payload 1861. The preamble 2271 includes the HT-STF 1712, the HT-LTF1714, the SIG-A field 916 f discussed above, and the extension field1012. In FIG. 22B, the extension field 1012 is illustrated as anextension SIG field comprising two symbols. The preamble 2271 optionallyincludes the one or more additional LTFs 1953.

in some aspects, the packet 2261 is used for open loop MIMOtransmission, in such aspects, the additional LTFs 1953 are omitted whenone spatial stream is used for the packet 2261. When additional spatialstreams are used, an additional LTF 1953 for each additional spatialstream may be included in the preamble 2271. In some aspects, 1, 2, or 4spatial streams may be used. In these aspects, 0, 1, or 2 additionalLTFs 1953 will be included in the preamble 2271.

In some aspects, an indicator in the extension field 1012 signifieswhether the additional LTFs 1953 are included. An example of such anindicator is described below with respect to FIG. 24.

With reference to FIG. 22C, the packet 2281 includes a preamble 2291 andthe payload 1861. The preamble 2291 includes the HT-STF 1712, the HT-LTF1714, the SIG-A field 916 f discussed above, the extension field 1012,and the precoded STF 1973. In FIG. 22C, the extension field 1012 isillustrated as an extension SIG field comprising two symbols. Thepreamble 2291 optionally includes the one or more precoded LTFs 1975.

In some aspects, the packet 2281 is used for MU-MIMO or Tx-BFtransmission. Indicators in the extension field 1012 may be used todifferentiate between such transmissions, as will be discussed inadditional detail below. In some aspects, the precoded LTFs 1975 areincluded when more than one spatial stream is used, similar to how theadditional LTFs 1953 are included in the packet 2261 when more than onespatial stream is used. The inclusion or omission of the precoded LTFs1975 may be indicated in the same way as the inclusion or omission ofthe additional LTF 1953.

In some aspects, a modulation of the SIG-A field 916 f is used toidentify whether the packet 2241 or either of the packets 2261, 2281 isbeing transmitted. For example, the wireless device 202 t may transmitthe SIG-A field 916 f using a rotated BPSK. When the wireless device 202r receives the SIG-A field 916 f, the wireless device 202 r maydetermine that either the packet 2261 or the packet 2281 is beingreceived. In order to differentiate between the packet 2261 and 2281,the wireless device 202 r may evaluate the extension field 1012. In someaspects, a QBPSK rotation is used to delineate between the packet 2241and either of the packets 2261, 2281. Thus, a rotation of the SIG-Afield 916 f may indicate that the extension field 1012 follows the SIG-Afield 916 e. The extension field 1012 may indicate whether an additionalLTF 1953, a precoded STF 1973, or the payload 1861 is next.

In some aspects, the processor 204 of the wireless device 202 (FIG. 2)determines to include the extension field 1012 when MIMO, STBC, or SU-BFis used. In some aspects, the processor 204 of the wireless device 202determines to include the extension field 1012 when the packet beingtransmitted is greater than 4096 bytes, a short GI is used, or alow-density parity-check (LDPC) code is used. Thus, the extension field1012 may be included for certain open loop SU modes short GI, STBC,MIMO, aggregation). In some aspects, A-MPDU is used when the extensionfield 1012 is included, and aggregation is not used when the extensionfield 1012 is omitted.

As discussed above, an open loop transmission may be used in thewireless communication system 100 of FIG. 1. For example, certainsensors configured for 802.11ah transmission may use an open looptransmission. Thus, in the second implementation, a packet includingonly five symbols in the preamble (e.g. the packet 2241) may be used fortypical sensor transmissions.

FIG. 23 illustrates an example of the SIG-A field 916 f. The SIG-A field916 f includes a length sub-field 2351 comprising 12 bits, an MCSsub-field 2353 comprising 4 bits, the bandwidth sub-field 2059, areserved sub-field 2355 comprising 1 bit, a parity sub-field 2357comprising 1 bit, and the tail sub-field 2075.

The length sub-field 2351 may indicate a length of the packet, or of thepayload of the packet, in which the SIG-A field 916 f is included. Thelength field 2351 may indicate the length of the packet in when theextension field 1012 is omitted. When the extension field 1012 isincluded, the length may be indicated in symbols. As discussed above,the inclusion of the extension field 1012 may be indicated by BPSKrotation of the SIG-A field 916 f. Thus, a modulation rotation of theSIG-A field 916 f may delineate whether the length field 2351 should beinterpreted as bytes or symbols.

The MCS sub-field 2353 indicates an MCS used for a user. If SU is beingused, the MCS is for the single user. If MU is being used, the MCS isfor one of the multiple users, for example, the first user.

FIG. 24 illustrates an example 1012 c of the extension field 1012. Inthe illustrated aspect, the extension field 1012 c comprises a twosymbol extension SIG field. The extension SIG field 1012 c includes anMCS sub-field 2451 comprising 12 bits, an N_(sts) sub-field 2453comprising 8 bits, a BF sub-field 2455 comprising 1 bit, an SGI/LGIsub-field 2457 comprising 1 bit, a coding sub-field 2459 comprising 4bits, an STBC sub-field 2461 comprising 1 bit, a GID sub-field 2463comprising 6 hits, a CRC sub-field 2465 comprising 4 bits, a reservedsub-field 2467 comprising 9 bits, and a tail sub-field 2469 comprising 6bits.

For MU transmissions, the MCS sub-field 2451 may indicate an MCS foreach of a plurality of users. In the illustrated aspect, there may be upto three users. As discussed above, an MCS for one user may be includedin the SIG-A field 916 f. The MCSs in the MCS sub-field 2451 may be forusers in addition to the user for which the MCS is included in the SIG-Afield 916 f. Thus, between the SIG-A field 916 f and the extension SIGfield 1012 c, MCS for four different users may be included.

For MU transmission, the N_(sts) sub-field 2453 may indicate a number ofspatial streams being used. For SU transmissions, however, the MCSsub-field 2451 in combination with the N_(sts) sub-field 2453 may beused to indicate an AID of the single user. For example, the bits of theMCS sub-field 2451 and six bits of the N_(sts) sub-field 2453 may carrythe AID.

The BE sub-field 2455, the SGI/LGI sub-field 2457, and the STBCsub-field 2461 may indicate whether beamforming is being used, whetheran SGI or LGI is being used, and whether STBC is being used,respectively. Thus, the BF sub-field 2455 may be used to distinguishbetween SU open loop transmissions and 3U-BF transmissions.

The GID sub-field 2463 may indicate a GID for devices to which a packetincluding the extension SIG field 1012 c is addressed. In some aspects,a value of the GID sub-field 2463 is reserved for SU open looptransmissions and/or a value of the GID sub-field 2463 is reserved forSU-BF transmissions. In such aspects, SU open loop an SU-BFtransmissions may be distinguished without evaluating the BF sub-field2455. In some such aspects, the BF sub-field 2455 is omitted.

The coding sub-field 2459 may indicate a coding for each of a pluralityof users. In the illustrated aspect, there may be up to four users. Inone aspect, each bit of the coding sub-field 2459 indicates a codingused for a respective user.

In some aspects, the SGI/LGI sub-field 2457 and/or the STBC sub-field2461 may be included in the SIG-A field 916 f rather than the extensionSIG field 1012 c. The STBC sub-field 2461 indicates an STBC for some orall spatial streams.

FIGS. 25A and 25B illustrate another implementation showing a pluralityof formats that may be used for the packet 1841 discussed above. Each ofthe formats illustrated in FIGS. 25A and 25B include an STF 912, an LTF914, and a SIG-A field 916. In this example, the LTF 914 and the SIG-Afield 916 each include four symbols. FIG. 25A illustrates an example ofa format of a packet, and FIG. 25B illustrates an example of anotherformat of a packet. The wireless device 202, may distinguish between thepackets of FIGS. 25A and 25B based on at least the LTF field 914.

With reference to FIG. 25A, the packet 2500 includes a preamble 2510 andthe payload 2520. The preamble 2510 includes STF 912, LTF 916, and SIG-Afield 916. The SIG-A field 916 may be repetition coded. These fields maybe similar to the corresponding fields discussed in this disclosure. Insome aspects, the packet 2500 is used for open loop transmissions overone spatial stream. For example, certain sensors configured for 802.11ahtransmission may utilize the packet 2500.

With reference to FIG. 25B, the packet 2550 includes a preamble 2560 andthe payload 2520. The preamble 2560 includes SIT 912, LTF 914, SIG-Afield 916, and extension field 1012. The SIG-A field 916 may berepetition coded. These fields may be similar to the correspondingfields discussed in this disclosure. In FIG. 25B, the extension field1012 is illustrated as an extension SIG field comprising three symbols.

In some aspects, the packet 2550 is used when advanced features, such asopen loop MIMO transmission, LDPC, single-user MIMO, Midamble, STBC, andPAID are used or when the payload is greater than 511 bytes. Theextension field 1012 of the packet 2550 may communicate information forthe advanced features. In some aspects, an indicator in the LTF field914 signifies whether the extension SIG field 1012 are included. Anexample of such an indicator is described below with respect to FIG. 26.

FIG. 26 illustrates an example of the SIG-A field 916 g. In theillustrated aspect, the SIG field 916 g comprises four symbols. TheSIG-A field 916 g includes a Length sub-field 2651 comprising 9 bits, anMCS sub-field 2653 comprising 4 bits, an SOI sub-field 2655 comprising 1bit, a 4-bit CRC sub-field 2657, and a 6-bit tail field 2659. In someembodiments, instead of the 4-bit CRC sub-field 2657, 1 parity bit and 3reserved bits may be included. Alternatively, in some aspects, ratherthan the 4-bit CRC sub-field 2657, 1 parity bit, 2 reserved bits, and1-bit Doppler/Midamble sub-field may be included.

The Length sub-field 2651 may indicate a length of the packet, or of thepayload of the packet, in which the SIG-A field 916 g is included. TheLength sub-field 2651 may indicate the length of the packet in byteswhen the extension field 1012 is omitted. When the extension field 1012is included, the length may be indicated in symbols. Whether theextension SIG field 1012 is included in the packet may be indicated bysymbol rotation of the LTF field 914 or a portion of the LTF field 914.For example, rotations of the last two symbols of the LTF field 914 mayindicate whether or not the extension SIG field 1012 is included. Thus,a modulation rotation of the LTF field 914 may delineate whether theLength sub-field 2651 should be interpreted as bytes or symbols.

The MCS sub-field 2653 may indicate a MCS for a user. If SU mode isbeing used, the MCS may be for the single user. If MU mode is beingused, the MCS may be for one of the multiple users, for example, thefirst user. The SGI sub-field 2655 may indicate where the short guardinterval is used. For instance, a short guard interval may be 2 μs and anormal guard interval may be 8 μs. In some aspects, a short guardinterval may be 2 μs and a normal guard interval may be 4 μs.

The SIG-A field 916 g may include the information needed for lss sensortraffic for payloads up to 511 bytes and include the information neededfor deferral. Therefore, devices not implementing advanced features mayshut-off after decoding the SIG-A field to save power.

FIG. 27 illustrates an example of the extension field 1012 d. In theillustrated example, the extension field 1012 d comprises a three symbolextension SIG field. The extension SIG field 1012 d includes a 2-bit SSsub-field 2751, a 1-bit Doppler/Midamble sub-field 2753, a 2 bit Codingsub-field 2755, a 5-bit PAID (partial association identifier) sub-field2757, a 1-bit STBC sub-field 2759, 1 parity sub-field 2761, and 6 tailsub-field 2763.

The num SS sub-field 2751 may indicate the number of spatial streamsused. The Doppler/Midamble sub-field 2753 may be included to indicatethat the receiver should mitigate the impact of high temporal channelvariation, or to indicate the presence of a midamble. The codingsub-field 2755 may indicate a coding for each of a plurality of users.In the illustrated aspect, there may be up to four users. In one aspect,each bit of the coding sub-field 2755 may indicate a coding used for arespective user.

The PAID sub-field 2757 includes a partial identifier for one or morereceivers. The PAID sub-field 2757 may be used by each receiver 202 r asan early indicator of whether the receiver should receive and decode theremainder of the packet. For example, if the PAID sub-field 2757indicates that the packet is not intended for a particular receiver, theparticular receiver may discontinue processing the packet in order tosave power. The STBC sub-field 2759 may indicate an STBC for one or morespatial streams. In some aspects, the parity sub-field 2761 covers onlythe extension SIG field 1012 d.

In some aspects, a SGI bit can be included in the extension SIG field1012 d instead of in the SIG-A field 916 g, and the Doppler/Midamble bitcan be included in the SIG-A field 916 g instead of in the extension SIGfield 1012. In some embodiments, the extension SIG field 1012 d includesfour symbols. In such embodiments the additional symbol may be included,for example, for reserved bits and/or additional PAID bits. Theadditional symbol may alternatively include other sub-fields.

The packets 2500 and 2550 of FIGS. 25A and 25B are particularlyadvantageous for 1 MHz transmission modes. The packet of FIG. 25A may besufficient for most traffic. In some embodiments, the longer packets ofFIG. 25B are used only when advanced features are used.

In some embodiments, the packets 2500 and 2550 of FIGS. 25A and 25B havealternate configurations. For example, in some embodiments, the SIG-Afield 916 g may be three symbols in length and the extension field 1012d may be only one symbol. In such embodiments, the three symbol SIG-Afield 916 g of may include a Length sub-field 2651 comprising 9 bits, anMCS sub-field 2653 comprising 3 or 4 bits, a 1 or 0 bit Coding sub-field2755, a SGI sub-field 2655 comprising 1 bit, and a 4-bit CRC sub-field2657. In some aspects, tail bits may be omitted when tail-bitingconvolutional codes are used. Further, a one symbol extension field 1012d may comprise a 2-bit SS sub-field 2751, a 1-bit Doppler/Midamblesub-field 2753, a 1 bit Coding sub-field 2755, a 1-bit STBC sub-field2759, and 1 parity sub-field 2761.

In some aspects, a payload, such as the payload 2520 of FIGS. 25A and25B, may be repetition coded. Whether the payload is repetition codedmay be indicated by symbol rotation of the LTF field 914 or a portion ofthe LTF field 914. For example, BPSK rotations of the last two symbolsof the LTF field 914 may indicate whether the payload is BPSK rate ½coded or is BPSK rate repetition coded. In some embodiments, if therotation of the LTF field 914 indicates that the payload is BPSK raterepetition coded, bits in a field of a preamble that may otherwise beused to indicate MCS of the payload may be used for another purpose,such as, but not limited to reserved bits, parity bits, or a CRC field.In some embodiments, a preamble includes a SIG field, which may be BPSKrate ½ 2× repetition encoded whenever the payload is BPSK rate ½ 2×repetition encoded, and may be BPSK rate ½ encoded whenever the payloadis not BPSK rate ½ 2× repetition encoded.

FIG. 28 illustrates an aspect of a method 2800 for transmitting apacket. The method 2800 may be used to selectively generate the packetsdiscussed in this disclosure, such as packets 700, 800 a, 800 b, 800 c,900, 1941, 2241, 1000, 1700, 1941, 1961, 2261, 2281, for example. Thepacket may be generated at the AP 104 or the STA 106 and transmitted toanother node in the wireless network 100. Although the method 2800 isdescribed below with respect to elements of the wireless device 202 t,other components may be used to implement one or inure of the steps.

At block 2802, it is determined whether to include an extension field ina physical layer preamble of a communication. The extension field maycomprise an extension SIG field and/or a SIG-B field, for instance. Insome aspects, a plurality of extension fields may be included. Thedetermination may be performed by the processor 204 and/or the DSP 220,for example. In some aspects, the processor 204 determines to includethe extension field when MU-MIMO is used, when the length of the packetwill be greater than a threshold amount, when a default mode is notbeing used for data, when the wireless device 202 t is not operating atone of two lowest bandwidths, or when the forward error correction (EEC)being used is not BCC.

At block 2804, the communication is generated. The communication maycomprise the physical layer preamble and a payload, and the preamble mayinclude a first field indicating whether the extension field isincluded. The first field may comprise a SIG field, for example, a SIG-Afield. The inclusion of the extension field may be indicated, forexample, by one or more bits in the SIG field, a BPSK rotation of theSIG field, and/or a bit on the Q-rail during a symbol of the SIG field.The generation may be performed by the processor 204 and/or the DSP 220,for instance. In some aspects, the processor 204 includes codingparameters for the payload in the first field when it is determined notto include the extension field, and includes coding parameters for thepayload in the extension field when it is determined to include theextension field. In some aspects, the coding parameters in an MCS may befor one or more users.

At block 2806, the packet is wirelessly transmitted. The transmissionmay be performed by the transmitter 210, for example.

FIG. 29 is a functional block diagram of an example wireless device 2900that may be employed within the wireless communication system 100 ofFIG. 1. The device 2900 comprises a determining module 2902 fordetermining whether to include an extension field in a physical layerpreamble of a communication. The determining module 2902 may beconfigured to perform one or more of the functions discussed above withrespect to the block 2802 illustrated in FIG. 28. The determining module2902 may correspond to one or more of the processor 204 and the DSP 220of FIG. 2, for instance. The device 2900 further comprises a generatingmodule 2904 for generating the communication. The generating module 2904may be configured to perform one or more of the functions discussedabove with respect to the block 2804 illustrated in FIG. 28. Thegenerating module 2904 may correspond to one or more of the processor204 and the DSP 220, for instance. The device 2900 further comprises atransmitting module 2906 for wirelessly transmitting the generatedcommunication. The transmitting module 2906 may be configured to performone or more of the functions discussed above with respect to the block2806 illustrated in FIG. 28. The transmitting module 2906 may correspondto the transmitter 210 of FIG. 2, for instance.

FIG. 30 illustrates an aspect of a method 3000 for receiving andprocessing a packet. The method 3000 may be used to receive and processthe packets discussed in this disclosure, such as packets 700, 800 a,800 b, 800 c, 900, 1941, 2241, 1000, 1700, 1941, 1961, 2261, 2281, forexample. The packet may be received at either the AP 104 or the STA 106from another node in the wireless network 100 of FIG. 1. Although themethod 3000 is described below with respect to elements of the wirelessdevice 202 r, other components may be used to implement one or more ofthe steps.

At block 3002, a wireless communication comprising a physical layerpreamble and a payload is received. The reception may be performed bythe receiver 212, for example. In some aspects, the preamble includes afirst field indicating whether the preamble also includes an extensionfield. The first field may comprise a SIG field, for example, a SIG-Afield. The inclusion of the extension field may be indicated, forexample, by one or more bits in the SIG field, a BPSK rotation of theSIG field, and/or a bit on the Q-rail during a symbol of the SIG field.The extension field may comprise an extension SIG field and/or a SIG-Bfield. In some aspects, a plurality of extension fields may be included.

At block 3004, the payload is processed based on modulation codingparameters included in the first field when the indicator signifies thatthe preamble does not include the extension field, and based on codingparameters included in the extension field when the indicator signifiesthat the preamble includes the extension field. The processing may beperformed by the processor 204, the signal detector 218, and/or the DSP220, for example. In some examples, the payload is processed using anMCS included in the first field and/or the extension field. In someaspects, when the extension field is included, the payload is processedby combining one or more sub-fields of the first field with one or moresub-fields of the extension field. In some aspects, the payload isprocessed for a plurality of users based on information in the extensionfield.

FIG. 31 is a functional block diagram of an example wireless device 3100that may be employed within the wireless communication system 100 ofFIG. 1. The device 3100 comprises a receiving module 3102 for wirelesslyreceiving a wireless communication comprising a physical layer preambleand a data unit. In some aspects, the preamble includes a first fieldindicating whether the preamble also includes an extension field. Thereceiving module 3102 may be configured to perform one or more of thefunctions discussed above with respect to the block 3002 illustrated inFIG. 30. The receiving module 3002 may correspond to the receiver 212 ofFIG. 2, for example. The device 3100 further comprises a processingmodule 3104 for processing the payload based on modulation codingparameters included in the first field. The processing module 3104 maybe configured to perform one or more of the functions discussed abovewith respect to the block 3004 illustrated in FIG. 30. The processingmodule 3104 may correspond to one or more of the processor 204, thesignal detector 218, and the DSP 220 of FIG. 2, for example. The device3100 further comprises a processing module 3106 for processing thepayload based on coding parameters included in the extension field. Theprocessing module 3104 may be configured to perform one or more of thefunctions discussed above with respect to the block 3004 illustrated inFIG. 30. The processing module 3106 may correspond to one or more of theprocessor 204, the signal detector 218 and the DSP 220 of FIG. 2, forexample.

FIG. 32 illustrates various components that may be utilized in thereceiver 212 of the wireless device 202 of FIG. 2. The componentsillustrated in FIG. 32 may be used to receive and distinguish betweenpackets, for example, such as the packets 900, 1000 and the packet 1100.

In the aspect illustrated in FIG. 32, the receiver 212 comprises a firstdetector 3202 and a second detector 3204. The first detector 3202 isconfigured to detect the STF 912, of FIG. 9, for instance. The seconddetector 3204 is configured to detect the SIT; 1112 of FIG. 11, forinstance. The first detector 3202 and the second detector 3204 may runin parallel to detect a packet and the format of the packet.

By using both the first detector 3202 and the second detector 3204, thereceiver 212 may auto-detect whether the packet 1100 is received, orwhether the packets 900, 1000 are received. If the first detector 3202detects that the packet 900 or 1000 is being received, the wirelessdevice 202 r may use one or more of the mechanisms described in thisdisclosure to determine whether the packet 900 or the packet 1000 isbeing received. The payload of a received packet may be processed basedon which of the packets 900-1100 are received and based on a SIG and/orextension field in the received packet. In this way, the wireless device202 r may be configured to receive and process packets that areformatted in multiple configurations as illustrated in FIGS. 9-11 forexample.

The processor of the wireless device 202 t may be configured to select,for instance, between the packets 900, 1000, and the packet 1100 basedon which packet includes a sequence repeated a greater number of timesthan in the packets 900 and 1000. Thus, a longer, more robust STY and/orpreamble may be transmitted when advantageous while maintaining the STFand/or preamble at an efficient length in other transmissions.

In addition to or in place of the STF detection described in thisdisclosure, the wireless device 202 r may distinguish, for instance,between the packets 900, 1000 and the packet 1100 using an auto-detectprocedure of the LTF. For example, when one of the symbols of the LTF1114 is flipped when compared to a respective symbol in the LTF 914, asdescribed in this disclosure, the wireless device 202 r may detectwhether a received packet is formatted as the packet 900 or 1000, or asthe packet 1100. In some such aspects, the STF may be formattedsimilarly in different packet formats. For example, the STF 912 in thepackets 900 and 1000 may be replaced by the STF 1112 in the packet 1100.In these aspects, a single detector may be implemented in the receiver212 to detect the start of a packet using the STF and the type of packetusing the LTF. In these aspects, however, packets may use the extendedSTF 1112, which may increase the length of the preamble.

FIG. 33 illustrates an example 1116 a of the SIG field 1116. The SIGfield 1116 a comprises a length sub-field 3302 including 10 bits, arepetition factor sub-field 3304 including 1 bit, a parity sub-field3306 including 1 bit, a reserved sub-field 3308 including 1 bit, and atail sub-field 3312 including 6 bits. The length sub-field 3302 mayindicate a length of the packet 1100 in bytes. The repetition factorsub-field 3304 may indicate a number of times that the plurality of bitsin the SIG field 1116 a is repeated. In the illustrated aspect, therepetition factor sub-field includes a bit which may be used to indicatewhether the plurality of bits in the SIG field 1116 is repeated twotimes or four times. If an 8× downclock factor is used for the preamble1110 and the plurality of bits may be repeated twice, the PHY rate maybe approximately 400 Kbps. In such an aspect, transmitting 1024 bytesmay take more than approximately 20 milliseconds.

The packets and fields illustrated in FIGS. 7-27 and 33 are examples andare not limiting on any of the packets or fields discussed in thisdisclosure. The packets and fields illustrated in FIGS. 7-27 and 33 mayinclude one or more additional fields or sub-fields or may omit one ormore fields or sub-fields.

FIG. 34 illustrates an aspect of a method 3400 for transmitting apacket. The method 3400 may be used to selectively generate the packetsillustrated in FIGS. 7, 8, 9, 10, 11, 17-19, 22, 25, for example. Thepacket may be generated at the AP 104 or the STA 106 and transmitted toanother node in the wireless network 100. Although the method 3400 isdescribed below with respect to elements of the wireless device 202 t,other components may be used to implement one or more of the steps.

At block 3402, a packet format is selected from at least two packetformats comprising a training field. In some aspects, the training fieldof one of the data packet formats includes a sequence repeated a greaternumber of times than in the training field of another of the data packetformats. In some aspects, the training field comprises an STF or LTF.The selection may be performed by the processor 204 and/or the DSP 220,for example.

At block 3404, a wireless communication is transmitted using theselected data packet format. The transmission may be performed by thetransmitter 210, for example.

FIG. 35 is a functional block diagram of another example wireless device3500 that may be employed within the wireless communication system 100of FIG. 1. The device 3500 comprises a selecting module 3502 forselecting a data packet format from at least two data packet formatscomprising a training field. The selecting module 3502 may be configuredto perform one or more of the functions discussed above with respect tothe block 3402 illustrated in FIG. 34. The selection module 3502 maycorrespond to one or more of the processor 204 and the DSP 220 of FIG.2, for example. The device 3500 further comprises a transmitting module3504 for transmitting a wireless communication using the selected packetformat. The transmitting module 3504 may be configured to perform one ormore of the functions discussed above with respect to the block 3404illustrated in FIG. 34. The transmitting module 3504 may correspond tothe transmitter 210 of FIG. 2, for example.

FIG. 36 illustrates an aspect of a method 3600 for receiving andprocessing a packet. The method 3600 may be used to receive and processthe packets illustrated in FIGS. 7, 8, 9, 10, 11, 17-19, 22, 25, forexample. The packet may be received at the AP 104 or the STA 106 fromanother node in the wireless network 100 of FIG. 1. Although the method3600 is described below with respect to elements of the wireless device202 r, other components may be used to implement one or more of thesteps.

At block 3602, a packet having one of at least two formats is wirelesslyreceived. The reception may be performed by the receiver 212, forexample. At block 3604, a format of the packet is detected using one ofat least two detectors configured to detect respective data packetformats. For example, the first detector 3202 and the second detector3204 of the receiver 212 may be used to detect either the packet format900 or the packet format 1100.

At block 3606, the received data packet is processed based on thedetected format. The processing may be performed by the processor 204,the signal detector 218, and/or the DSP 220, for example.

FIG. 37 is a functional block diagram of another example wireless device3700 that may be employed within the wireless communication system 100.The device 3700 comprises a receiving module 3702 for wirelesslyreceiving a packet having one of at least two formats. The receivingmodule 3702 may be configured to perform one or more of the functionsdiscussed above with respect to the block 3602 illustrated in FIG. 36.The receiving module 3702 may correspond to the receiver 212 of FIG. 2,for example. The device 3700 further comprises a first detecting module3704 for detecting whether the received data packet has a first format.The first detecting module 3704 may be configured to perform one or moreof the functions discussed above with respect to the block 3604illustrated in FIG. 36. The first detecting module 3704 may correspondto the first detector 3202 in the receiver 212 of FIG. 32, for example.The device 3700 further comprises a second detecting module 3706 fordetecting whether the received data packet has a second format. Thesecond detecting module 3706 may be configured to perform one or more ofthe functions discussed above with respect to the block 3604 illustratedin FIG. 36. The second detecting module 3706 may correspond to thesecond detector 3204 in the receiver 212 of FIG. 32, for example. Thedevice 3700 further comprises a processing module 3708 for processingthe packet based on the first detecting module 3704 and the seconddetecting module 3706. The processing module 3708 may be configured toperform one or more of the functions discussed above with respect to theblock 3606 illustrated in FIG. 36. The processing module 3708 maycorrespond to one or more of the processor 204, the signal detector 218,and the DSP 220 of FIG. 2, for example.

FIG. 38 illustrates an aspect of a method 3800 for receiving a portionof a packet. The method 3800 may be used to receive a physical layerpreamble of the packet and cease further processing of the packet afterdetermining that the packet is not intended for the device that receivedthe packet. The packet may be received at the AP 104 or the STA 106 fromanother node in the wireless network 100 of FIG. 1. Although the method3800 is described below with respect to elements of the wireless device202 r, other components may be used to implement one or more of thesteps.

At block 3802, at least the preamble of a packet is wirelessly received.The reception may be performed by the receiver 212, for example. In someaspects, the preamble includes a first field indicating whether thepreamble also includes an extension field. The first field may comprisea SIG field, for example a SIG-A field. The inclusion of the extensionfield may be indicated, for example, by one or more bits in the SIGfield, a BPSK rotation of the SIG field, and/or a bit on the Q-railduring a symbol of the SIG field. The extension field may comprise anextension SIG field and/or a SIG-B field. In some aspects, a pluralityof extension fields may be included.

At block 3804, reception of a remainder of the packet is aborted whenthe first field indicates that the preamble includes the extensionfield. The aborting may be performed by the processor 204, the receiving212, the signal detector 218, and/or the DSP 220, for example. In thisway, power that may otherwise be used to fully receive and/or processthe packet may be conserved.

FIG. 39 is a functional block diagram of another example wireless device3900 that may be employed within the wireless communication system 100.The device 3900 comprises a receiving module 3902 for wirelesslyreceiving at least a physical layer preamble of a wirelesscommunication. In some aspects, the preamble includes a first fieldindicating whether the preamble also includes an extension field. Thereceiving module 3902 may be configured to perform one or more of thefunctions discussed above with respect to the block 3802 illustrated inFIG. 38. The receiving module 3902 may correspond to the receiver 212 ofFIG. 2, for example. The device 3900 further comprises an abortingmodule 3904 for aborting reception of a remainder of the packet when thefirst field indicates that the preamble includes the extension field.The aborting module 3904 may be configured to perform one or more of thefunctions discussed above with respect to the block 3804 illustrated inFIG. 38. The aborting module 3904 may correspond to one or more of theprocessor 204, the receiver 212, the signal detector 218, and the DSP220 of FIG. 2, for example.

FIG. 40 illustrates an aspect of a method 4000 for transmitting apacket. The method 4000 may be used to generate the packets discussed inthis disclosure, such as packets 2500 and 2550, for example. The packetmay be generated at the AP 104 or the STA 106 and transmitted to anothernode in the wireless network 100. Although the method 4000 is describedbelow with respect to elements of the wireless device 202 t, othercomponents may be used to implement one or more of the steps.

At block 4002, a wireless communication comprising a physical layerpreamble and payload is generated. The preamble includes a LTFindicating whether the payload includes data which is repetition coded.For instance, the indication may be provided by symbol rotation of theLTF or a portion of the LTF. The generation may be performed by theprocessor 204 and/or the DSP 220, for example.

At block 4004, the generated communication is transmitted wirelessly.The transmission may be performed by the transmitter 210, for example.

FIG. 41 is a functional block diagram of an example wireless device 4100that may be employed within the wireless communication system of FIG. 1.The device 4100 comprises a generating module 4102 for generating awireless communication including a physical layer preamble and apayload. The preamble may include a LTF indicating whether the payloadincludes data which is repetition coded. The generating module 4102 maybe configured to perform one or more of the functions discussed abovewith respect to the block 4002 illustrated in FIG. 40. The generatingmodule 4102 may correspond to one or more of the processor 204 and theDSP 220 of FIG. 2, for instance. The device 4100 further comprises atransmitting module 4104 for wirelessly transmitting the generatedcommunication. The transmitting module 4104 may be configured to performone or more of the functions discussed above with respect to the block4004 illustrated in FIG. 40. The transmitting module 4104 may correspondto the transmitter 210 of FIG. 2, for instance.

FIG. 42 illustrates an aspect of a method 4200 for receiving a portionof a packet. The method 4200 may be used to receive and process thepackets discussed in this disclosure, such as packets 2500 and 2550, forexample. The packet may be received at either the AP 104 or the STA 106from another node in the wireless network 100. Although the method 4200is described below with respect to elements of the wireless device 202r, other components may be used to implement one or more of the steps.

At block 4202, a wireless communication comprising a physical layerpreamble and a payload is received. The reception may be performed bythe receiver 212, for example.

At block 4204, the payload is processed based on a LTF included in thepreamble that indicates whether the payload includes data which isrepetition coded. For instance, the indication may comprise a symbolrotation of the LTF or a portion of the LTF. The processing may beperformed by the processor 204, the signal detector 218, and/or the DSP220, for example.

FIG. 43 is a functional block diagram of an example wireless device 4300that may be employed within the wireless communication system of FIG. 1.The device 4300 comprises a receiving module 4302 for receiving awireless communication comprising a physical layer preamble and apayload. The receiving module 4302 may be configured to perform one ormore of the functions discussed above with respect to the block 4202illustrated in FIG. 42. The receiving module 4302 may correspond to thereceiver 212 of FIG. 2, for example. The device 4200 further comprises aprocessing module 4304 for processing the payload based on a LTFincluded in the preamble that indicates whether the payload includesdata which is repetition coded. The processing module 4304 may beconfigured to perform one or more of the functions discussed above withrespect to block 4204 illustrated in FIG. 42. The processing module 4304may correspond to one or more of the processor 204, the signal detector218, and the DSP 220 of FIG. 2, for example.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like. Further, a “channel width” as used herein may encompass ormay also be referred to as a bandwidth in certain aspects.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: b, or c” is intended to cover: a, b, c,a-b, a-c, b-o, and a-b-c.

The various operations of methods described above may be performed byany suitable means capable of performing the operations, such as varioushardware and/or software component(s), circuits, and/or module(s).Generally, any operations illustrated in the Figures may be performed bycorresponding functional means capable of performing the operations.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array signal (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware componentsor any combination thereof designed to perform the functions describedherein. A general purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

In one or more aspects, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can comprise RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Thus, in some aspects computer readable medium may comprisenon-transitory computer readable medium tangible media). In addition, insome aspects computer readable medium may comprise transitory computerreadable medium (e.g., a signal). Combinations of the above should alsobe included within the scope of computer-readable media.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware or any combination thereof. If implemented in software, thefunctions may be stored as one or more instructions on acomputer-readable medium. A storage media may be any available mediathat can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM.CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition oftransmission medium.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

While the foregoing is directed to aspects of the present disclosure,other and further aspects of the disclosure may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An apparatus for wireless communication, comprising: a receiverconfigured to receive at least a physical layer preamble of a wirelesscommunication, the preamble including a first field indicating whetherthe preamble includes an extension field; and a processor configured toabort reception of a remainder of the communication when the first fieldindicates that the preamble includes the extension field.
 2. Theapparatus of claim 1, wherein the first field comprises a signal (SIG)field.
 3. The apparatus of claim 2, wherein a bit in the SIG fieldindicates whether the extension field is included.
 4. The apparatus ofclaim 2, wherein two bits in the SIG field indicate whether theextension field is included.
 5. The apparatus of claim 2, wherein arotation of a modulation of the SIG field indicates whether theextension field is included.
 6. The apparatus of claim 2, wherein anindication on a quadrature phase during a symbol of the SIG fieldindicates whether the extension field is included.
 7. The apparatus ofclaim 1, wherein the preamble comprises an SIT field and a 4-symbolSIG-A field, and the first field comprises a 4-symbol LTF field.
 8. Theapparatus of claim 7, wherein the SIG-A field includes a Lengthsub-field comprising 9 bits, an MCS sub-field comprising 4 bits, an SGIsub-field comprising 1 bit, a parity bit, 3 reserved bits, and a 6-bittail field.
 9. The apparatus of claim 7, wherein the SIG-A fieldincludes a Length sub-field comprising 9 bits, an MCS sub-fieldcomprising 4 bits, an SGI sub-field comprising 1 bit, a parity bit, 2reserved bits, a 1-bit Doppler/Midamble sub-field, and a 6-bit tailfield.
 10. The apparatus of claim 7, wherein the SIG-A field includes aLength sub-field comprising 9 bits, an MCS sub-field comprising 4 bits,an SGI sub-field comprising 1 bit, a 4-bit CRC sub-field, and a 6-bittail field.
 11. The apparatus of claim 7, wherein the LTF field includesinformation which indicates whether the preamble includes the extensionfield.
 12. The apparatus of claim 11, wherein a symbol rotation of theLTF field or a portion of the LTF field indicates whether the extensionfield is included.
 13. The apparatus of claim 12, wherein rotations ofthe last two symbols of the LTF field indicate whether the extensionfield is included.
 14. The apparatus of claim 7, wherein the Lengthsub-field indicates a length of the payload or of the payload and thepreamble, wherein the Length field indicates the length in bytes if theextension field is omitted, and indicates the length in symbols if theextension field is included.
 15. The apparatus of claim 7, wherein theSIG-A field includes information for sensor traffic having payloads upto 511 bytes, and includes information for deferral.
 16. The apparatusof claim 7, wherein the SIG-A field includes a Length sub-fieldcomprising 9 bits, an MCS sub-field comprising 4 bits, aDoppler/Midamble sub-field comprising 1 bit, a parity bit, 3 reservedbits, and a 6-bit tail field and the extension field includes a 2-bit SSsub-field, a 1-bit SGI sub-field, a 2 bit Coding sub-field, a 5-bit PAIDsub-field, a 1-bit STBC sub-field, 1 parity bit, and 6 tail bits. 17.The apparatus of claim 1, wherein the extension field includesinformation for advanced features.
 18. The apparatus of claim 17,wherein the advanced features include at least one of open loop MIMOtransmission, LDPC, single-user MIMO, use of a Midamble, use of STBC,and use of PAID.
 19. The apparatus of claim 1, wherein the extensionfield includes information for the payload, and the payload is greaterthan 511 bytes.
 20. The apparatus of claim 1, wherein the extensionfield includes three symbols.
 21. The apparatus of claim 1, wherein theextension field includes a 2-bit SS sub-field, a 1-bit Doppler/Midamblesub-field, a 2 bit Coding sub-field, a 5-bit PAID sub-field, a 1-bitSTBC sub-field, 1 parity bit, and 6 tail bits.
 22. The apparatus ofclaim 1, wherein the extension field includes four symbols.
 23. Theapparatus of claim 22, wherein the extension field includes reservedbits or more than 5 PAID bits.
 24. The apparatus of claim 1, whereininclusion of the extension field indicates that aggregation is to beenforced.
 25. A method of wireless communication, comprising: receivingat least a physical layer preamble of a wireless communication, thepreamble including a first field indicating whether the preambleincludes an extension field; and aborting reception of a remainder ofthe communication when the first field indicates that the preambleincludes the extension field.
 26. The method of claim 25, wherein thefirst field comprises a signal (SIG) field.
 27. The method of claim 26,wherein a bit in the SIG field indicates whether the extension field isincluded.
 28. The method of claim 26, wherein two bits in the SIG fieldindicate whether the extension field is included.
 29. The method ofclaim 26, wherein a rotation of a modulation of the SIC field indicateswhether the extension field is included.
 30. The method of claim 26,wherein an indication on a quadrature phase during a symbol of the SICfield indicates whether the extension field is included.
 31. The methodof claim 25, wherein the preamble comprises an STF field and a 4-symbolSIC-A field, and the first field comprises a 4-symbol LTF field.
 32. Themethod of claim 31, wherein the SIG-A field includes a Length sub-fieldcomprising 9 bits, an MCS sub-field comprising 4 bits, an SGI sub-fieldcomprising 1 bit, a parity bit, 3 reserved bits, and a 6-bit tail field.33. The method of claim 31, wherein the SIC-A field includes a Lengthsub-field comprising 9 bits, an MCS sub-field comprising 4 bits, an SGIsub-field comprising 1 bit, a parity bit, 2 reserved bits, a 1-bitDoppler/Midamble sub-field, and a 6-bit tail field.
 34. The method ofclaim 31, wherein the SIG-A field includes a Length sub-field comprising9 bits, an MCS sub-field comprising 4 bits, an SGI sub-field comprising1 bit, a 4-bit CRC sub-field, and a 6-bit tail field.
 35. The method ofclaim 31, wherein the LTF field includes information which indicateswhether the preamble includes the extension field.
 36. The method ofclaim 35, wherein a symbol rotation of the LTF field or a portion of theLTF field indicates whether the extension field is included.
 37. Themethod of claim 36, wherein rotations of the last two symbols of the LTFfield indicate whether the extension field is included.
 38. The methodof claim 31, wherein the Length sub-field indicates a length of thepayload or of the payload and the preamble, wherein the Length fieldindicates the length in bytes if the extension field is omitted, andindicates the length in symbols if the extension field is included. 39.The method of claim 31, wherein the SIG-A field includes information forsensor traffic having payloads up to 511 bytes, and includes informationfor deferral.
 40. The method of claim 31, wherein the SIG-A fieldincludes a Length sub-field comprising 9 bits, an MCS sub-fieldcomprising 4 bits, a Doppler/Midamble sub-field comprising 1 bit, aparity bit, 3 reserved bits, and a 6-bit tail field and the extensionfield includes a 2-bit SS sub-field, a 1-bit SGI sub-field, a 2 bitCoding sub-field, a 5-bit PAID sub-field, a 1-bit STBC sub-field, 1parity bit, and 6 tail bits.
 41. The method of claim 25, wherein theextension field includes information for advanced features.
 42. Themethod of claim 41, wherein the advanced features include at least oneof open loop MIMO transmission, LDPC, single-user MIME), use of aMidamble, use of STBC, and use of PAID.
 43. The method of claim 25,wherein the extension field includes information for the payload, andthe payload is greater than 511 bytes.
 44. The method of claim 25,wherein the extension field includes three symbols.
 45. The method ofclaim 25, wherein the extension field includes a 2-bit SS sub-field, a1-bit Doppler/Midamble sub-field, a 2 bit Coding sub-field, a 5-bit PAIDsub-field, a 1-bit STBC sub-field, 1 parity bit, and 6 tail bits. 46.The method of claim 25, wherein the extension field includes foursymbols.
 47. The method of claim 46, wherein the extension fieldincludes reserved bits or more than 5 PAID bits.
 48. The method of claim25, wherein inclusion of the extension field indicates that aggregationis to be enforced.
 49. An apparatus for wireless communication,comprising: means for receiving at least a physical layer preamble of awireless communication, the preamble including a first field indicatingwhether the preamble includes an extension field; and means for abortingreception of a remainder of the communication when the first fieldindicates that the preamble includes the extension field.
 50. A computerreadable medium comprising instructions that when executed cause anapparatus to: receive at least a physical layer preamble of a wirelesscommunication, the preamble including a first field indicating whetherthe preamble includes an extension field; and abort reception of aremainder of the communication when the first field indicates that thepreamble includes the extension field.